Skull and Brain


  • skull = calvarium + facial bones + mandible
  • calvarium = skull vault + skull base


    • epicranial/galea aponeurosis  (covers upper cranium)
    • pericranium (external periosteum)
    • endosteum (internal periosteum, external layer of dura)
    • tables = diploe
    • diploic veins (between tables)
    • emissary veins (traverse tables)
    • venous lacunae (communicate with superior sagittal sinus)
    • superior sagittal sinus (intradural)
    • arachnoid/Pacchionian granulations
    • intrasutural/Wormian bones (in suture lines)


Skull vault:

  • metopic suture (fuses 2y; persistent V10%)
  • bregma = anterior fontanelle (closes 2y)
  • sagittal suture
  • lambda = posterior fontanelle (closes 6/12)
  • coronal/frontoparietal suture
  • pterion (junction of frontal, sphenoid, parietal and temporal bones)
  • sphenofrontal and sphenoparietal sutures
  • sphenosquamosal suture (sphenoid and temporal bones)
  • anterolateral and posterolateral fontanelles (closes 3/12)
  • squamosal/parietotemporal suture
  • squamous temporal bone
  • asterion = mastoid fontanelle (junction squamosal and lambdoid sutures; closes 2y)
  • lambdoid/parietooccipital suture
  • mendosal/accessory suture (in occipital bone)
  • parietal foramina (post-med-sup) with emissary vv of Santorini

Skull Base

Anterior cranial fossa:

  • orbital plates of the frontal bone
  • ethmoid bone (cribriform plate, crista galli)
  • foramen cecum (ant to crista galli; emissary v to superior sag sinus)
  • foramina of cribriform plate (CNI)
  • anterior and posterior ethmoidal foramen (ant and posterior ethmoidal a&v&n)
  • jugum/planum sphenoidale (ant part of sphenoid body)
  • lesser wing of sphenoid with sphenoid ridge (ant-sup, continuous with jugum and anterior clinoid process)
  • innominate line on XR (curving greater wing of sphenoid, over orbit)
  • superior orbital foramen (CN3,4,V1,6, superior orbital v, branch of middle meningeal a)
  • sphenoid ridge (post lesser wing)

Middle cranial fossa:

  • petroclinoid and interclinoid ligaments (dural reflections, often calcify)
  • anterior clinoid process
  • optic canal
  • sphenoid body = basisphenoid – from ant –> post: jugum (ant cranial fossa), optic/prechiasmatic groove (= sulcus chiasmaticus), sella turcica (tubuerculum sellae, pituitary/hypophyseal fossa, dorsum sellae, posterior clinoid process)
    • J-shaped/omega/hour-glass sella (V5%, elongation of sella turcica with prominent sulcus chiasmaticus)
  • lamina dura (floor of sella turcica)
  • carotid groove/sulcus (lat body)
  • foramen rotundum (CNV2; -> pterygopalatine fossa)
  • foramen ovale (CNV3, acc meningeal a, lesser petrosal n; –> infratemporal fossa)
  • foramen spinosum (middle meningeal a&v, meningeal branch of V3; -> infratemporal fossa)
  • Meckle’s/trigeminal cave
  • Vidian/pterygoid canal (ant to foramen lacerum -> posterior pterygopalatine fossa; a&n of pterygoid canal [greater and deep petrosal nn > pterygopalatine ganglion])
  • foramen of Vesalius/sphenoid emissary foramen
  • foramen lacerum (cartilage, small emissary vv, at medial aspect of carotid canal)
  • petrous temporal bone
  • carotid canal
  • petrous apex
  • squamous temporal bone
  • zygomatic process
  • mandibular condylar fossa
  • mastoid process
  • external auditory canal
  • styloid process
  • stylomastoid foramen (CNVII)
  • petrous ridge (w groove for superior petrosal sinus)

Posterior cranial fossa:

  • clivus = basion + posterior sphenoid body, basisphenoid/sphenoccipital synchondrosis (fuses at puberty)
  • occipital bone
  • basiocciput = basion (compact bone)
  • foramen magnum (~ 35 x 30 mm)
  • opisthion (post to foramen magnum, compact bone)
  • squamous occipital bone
  • external and internal occipital protuberances
  • internal acoustic meatus (CN7,8, internal auditory a)
  • occipital condyles
  • hypoglossal/anterior condylar canal (CN12), between jugular foramen and foramen magnum
  • jugular foramen, divided by the jugular spur
    • pars nervosa (ant-med; CNIX, inferior petrosal sinus)
    • pars vascularis (CNX,XI, jugular bulb)
  • condylar canal (post to jugular foramen; emissary v and meningeal br of ascending pharyngeal a)


Dura mater (pachymeninges):

  • outer periosteum layer
  • inner dura layer proper – separates from outer layer around dural venous sinuses and falx/tentorium/diaphragm sella. Lined by mesothelium.
  • falx cerebri (-> crista galli, superior sagittal sinus; inferior sag sinus in free edge)
  • diaphragma sellae (roof of hypophyseal fossa)
  • supratentorial compartment
  • tentorium cerebelli (-> post clinoid process, upper border petrous bones, margins of transverse sinuses, internal occipital protuberance)
  • tentorial hiatus/incisura/notch (->ant clinoid processes, dural venous confluence; may compress uncus and PCA with high pressure)
  • trigeminal cave (outpouching of tentorium surrounding trigeminal nerve and ganglion)
  • infratentorial compartment
  • falx cerebelli (->internal occipital protuberance, internal occipital crest around small occipital venous sinus, posterior foramen magnum)
  • subdural potential space contains bridging veins (cortex -> venous sinuses and arachnoid villi)

Arachnoid mater: leptomeninges = arachnoid + pia mater

  • separated from dura by lymph in subdural (potential) space
  • projects into interhemispheric fissure, root of sylvian fissure, venous sinuses and lakes as arachnoid villi (only place where it is pervious to CSF)

Pia mater:

  • subarachnoid space with CSF
  • closely adherent to brain surface and contains vast network of vessels; -> epineurium; invaginates into brain with choroid vessels into ventricles, cerebral aa

Vascular and Nerve Supply:

  • arteries between layers of dura
  • middle meningeal artery -> foramen spinosum -> middle cranial fossa -> anterior and posterior branches
  • accessory meningeal artery -> foramen ovale
  • meningeal branches of ophthalmic and ant/post ethmoidal aa
  • meningeal branches of ICA, vertebral a, occipital a (via mastoid and jugular foramina), ascending pharyngeal a (via jugular foramen, hypoglossal canal)
  • V1,V2,V3 -> supratentorial meninges
  • meningeal branches of CNIX,X,C1-C3 -> posterior cranial fossa

Cerebral Hemispheres

Frontal, parietal, occipital and temporal lobes

Corpus Callosum (~10cm)

  • corpus callosum (forms genu->splenium then rostrum; partial or complete agenesis [V])
  • rostrum (ant-inf)
  • genu (ant)
  • body/trunk of corpus callosum
  • splenium (post)
  • forceps minor (frontal radiation corpus callosum)
  • tapetum (temporal radiation)
  • forceps major (occipital radiation of corpus callosum)


  • A = frontal lobe
  • P = occipital lobe
  • S = falx cerebri, inferior sagittal sinus
  • lateral = tapetum

Gyri and Sulci

Superficial aspect:

  • Sylvian/lateral fissure
  • orbital, frontal (contains portion of Broca’s motor speech area), parietal (A->P) and temporal operculum
  • insula cortex = island/isle of Reil; inferior part = limen of insula
  • frontal pole
  • superior, middle and inferior frontal gyri. Inferior fontal gyrus contains (P->A) opercular, triangular and orbital parts.
  • superior and inferior frontal sulci
  • premotor cortex (Broca’s speech area = post/inf in dominant hemisphere)
  • precentral sulcus
  • precentral gyrus (motor cortex)
  • central sulcus = Rolandic fissure (just posterior to the anterior limit of lateral ventricles)
    • superior frontal sulcus ends at precentral sulcus
    • interparietal sulcus ends at postcentral sulcus
    • cingulate sulcus -> marginal sulcus (post to central sulcus)
    • sup-med end of postcentral sulcus shaped like bifid Y
    • ascending ramus of Sylvian fissure -> precentral sulcus
    • precentral gyrus cortical grey matter thicker than postcentral gyrus by ~1.5:1
    • pericentral cortex less intense on FLAIR
  • postcentral gyrus (somatic sensory cortex)
  • postcentral sulcus
  • parietal association cortex
  • superior parietal lobule
  • intraparietal sulcus
  • inferior parietal lobule
    • supramarginal gyrus (sup continuation of superior temporal gyrus)
    • angular gyrus (sup continuation of middle temporal gyrus)
  • occipital pole
  • temporo-occipital incisura = preoccipital notch
  • superior (auditory cortex with posterior Wernicke’s area in dominant hemisphere = L in 97%), middle and inferior temporal gyri
  • temporal association cortex (around auditory cortex)
  • superior and inferior temporal sulci

Medial aspect:

  • callosal sulcus = sulcus of corpus callosum
  • cingulate gyrus
  • cingulate sulcus (continues posterior with marginal sulcus)
  • medial frontal gyrus
  • paracentral sulcus (med, anterior to central sulcus)
  • paracentral lobule
  • marginal sulcus (post to central sulcus, cont anterior with cingulate sulcus and superior with postcentral sulcus)
  • precuneus
  • parieto-occipital fissure/sulcus
  • cuneus
  • calcarine sulcus
  • calcarine gyrus
  • visual cortex (surrounds calcarine sulcus)
  • occipital association cortex (ant to visual cortex)

Inferior aspect:

  • uncus (ant-med temporal lobe)
  • parahippocampal gyrus
  • collateral sulcus (lat to parahippocampal gyrus)
  • medial and lateral occipitotemporal gyri (med = continuation with parahippocampal)
  • straight gyrus = gyrus rectus
  • olfactory sulcus
  • orbital gyri and sulci


Diencephalon and Pituitary Gland

diencephalon = thalamus + hypothalamus + epithalamus (pineal gland , habenular)


  • relays sensory pathways, limbic outputs, coordination of movement
  • anterior nuclei (with apex), median nuclei (with interthalamic adhesion) and lateral nuclei (with pulvinar [post], medial and lateral geniculate bodies)
  • interthalamic adhesion = massa intermedia (in 60%)
  • lateral geniculate body (ant; –> sup colliculus, visual pathway)
  • medial geniculate body (post; –> inf colliculus, auditory pathway)


  • superior = floor lateral ventricle
  • medial = 3rd ventricles
  • lateral = internal capsule, lentiform, body and tail caudate


  • floor of 3rd ventricle
  • optic chiasm
  • tuber cinereum (grey matter between chiasm and infundibulum), inferior extension of the thalamus, connects to the infundibulum.
  • infundibulum = pituitary stalk (diameter < basilar a)
  • mamillary bodies (ant to basilar artery and posterior perforated substance)
  • posterior perforated substance (interpeduncular fossa, pieced by branches of PCA)


  • habenular commisure = superior lamina (often calcified, sup to quadrigeminal plate)
  • pineal gland/body (calcifies 2% <8yo, most >30yo; A = thalamus; S = cerebral vv, splenium; I = superior colliculi)
  • posterior commisure = inferior lamina (connects superior colliculi, concerned with light reflexes)
  • AC-PC line
  • anterior commisure (connecting olfactory tracts, amygdalas and temporal lobes)
  • lamina terminalis (between AC and optic chiasm)

Pituitary Gland

(Hypophysis cerebri)

  • 12 x 8 x 9mm, directed ant-inf
  • adenohypophysis = anterior lobe. Hypophyseal portal vv (from capillary bed in infundibulum) stimulates hormones including prolactin, growth hormone, thyroid stimulating hormone, follicle stimulating hormone, and leutinizing hormone. Indirectly supplied via superior hypophyseal (from supraclinoid ICA) -> plexus around base of hypophyseal stalk and median eminence of tuber cinereum -> portal system to anterior pituitary.
    • pars tuberalis (ant to stalk)
    • pars intermedia (post), contains small cysts
    • pars distalis (ant, most of the adenohypophysis)
  • neurohypophysis – consists of posterior lobe, infundibular stem and median eminence. Stores antidiuretic hormone and oxytocin. Supplied directly from inferior hypophyseal a (from meningohypophyseal trunk of cavernous ICA).


  • S = diaphragm sella (dura), suprasellar cistern, optic chiasm, COW
  • I = body sphenoid, sphenoid sinus
  • lateral = cavernous sinus (middle: ICA and CNVI; lateral wall S->I: CNIII,IV,V1,V2)
  • A+P+I = intercavernous sinus

Basal Ganglia/Nuclei

Coordination of smooth movement. Corpus striatum (caudate and putamen) + globus pallidus + amygdaloid body + claustrum + substantia nigra

  • head, body (sup-lat of lateral ventricle) and tail (ant/lat trigone-> sup-lat temporal horn) of caudate -> amygdaloid body
  • internal capsule
    • anterior limb (frontopontine fibres, thalamocortical fibres; recurrent artery of Heubner [ACA])
    • genu (motor fibres of head, corticobulbar fibres; lenticulostriate arteries [MCA])
    • posterior limb (A->P motor fibres arm, hand, trunk, leg, perineum; parietopontine, occipitopontine fibres, sensory fibres, visual fibres, auditory fibres; anterior choroidal artery [ICA])
  • lentiform nucleus (globus pallidus [med] + putamen [lat])
  • external capsule
  • claustrum (grey matter)
  • extreme capsule
  • insular cortex

Limbic System

Emotional responses to visceral stimuli, memory function. Communications with olfactory and gustatory systems.

limbic lobe (limbic and intralimbic gyri)

  • limbic gyrus (subcallosal, cingulate gyri, isthmus, parahippocampal gyrus, uncus)
    • subcallosal/parolfactory/paraterminal gyrus = peduncle of corpus callosum (ant to lamina terminalis)
    • cingulate gyrus
    • isthmus of cingulate gyrus = splenial gyrus (narrowing post/inf to splenium of corpus callosum)
    • parahippocampal gyrus. (Fornicate gyrus = parahippocampal and cingulate gyri)
      • posterior segment, containing the subiculum on its superomedial surface
      • anterior segment (piriform lobe) containng the uncus and entorhinal area.
    • amygdala deep within the uncus, primary cortex for emotions. Inputs from olfactory system, thalami and hypothalamus. Abnormality may cause anhedonia (lack of emotional responses)
  • outer intralimbic gyrus (indusium grisem, dentate gyrus, hippocampus)
    • indusium griseum = supracallosal gyrus = gyrus epicallosus (grey matter on corpus callosum) with medial and lateral longitudinal striae (white matter)
    • grey matter of parahippocampal gyrus: enterorhinal cortex -> parasubiculum -> subiculum proper (sup-med to parahippocampal gyrus) –> presubiculum
    • hippocampal sulcus
    • hippocampus (dentate gyrus + cornua ammonis). Visceral responses to emotions, memory.
      • head of hippocampus = pes hippocampi
      • tail of hippocampus
      • dentate gyrus (med, at apex of horn)
      • Ammon’s horn = cornua ammonis (continuation of subiculum, cuving med). Zones: CA1 (Sommer/vunerable sector, lat; most sensitive area of brain to anoxia along with globus pallidus), CA2 (dorsal resistant zone, sup), CA3 (Spleilmeyer sector, sup-med), CA4 (end folium, inf-med).
  • inner intralimbic gyrus (fimbria, fornix)
    • alveus hippocampi (white band fornix fibres covering ventricular surface of hippocampus)
    • fimbria of hippocampus (fibres from alveus converge on medial hippocampus)
    • crura = posterior pillars of fornix
    • body of fornix (single, inferior to posterior corpus callosum and septum pellucidum)
    • columns of fornix (paired, anterior to interventricular foramen, between foramen and anterior commissure)
    • mammillary bodies (post to optic chiasm and tuber cinerium)
    • habenular fibres (column -> over thalamus -> habenular commissure)

File:Hippocampus (brain).jpg


Medulla Oblongata

  • open and closed medulla
  • obex (bottom angle of open medulla)
  • anterior/ventral median fissure/sulcus
  • pyramids (med) with decussation of pyramids (lower medulla, obliterationg anterior median fissure)
  • anterolateral/preolivary sulcus
  • olives (lat)
  • postolivary sulcus
  • pontomedullary sulcus
  • posterior/dorsal median sulcus
  • gracile (med) tubercle continuing inferior as fasciculus
  • posterolateral sulcus
  • cuneate (lat) tubercle and fasciculus
  • gracile and cuneate nuclei -> internal arcuate fibres -> decussate -> medial lemnisci (->thalamus -> cortex)
  • inferior medullary velum
  • rhomboid fossa (floor of 4th ventricle)
    • medial eminence with (S->I) facial colliculi, striae medullares, hypoglossal trigone, vagal trigone
  • contains nuclei for IX-XII

Vascular supply:

  • anterior medulla – vertebral and basilar aa, inferior petrosal sinus
  • posterior medulla – PICA, occipital sinus
  • inferior medullary v -> spinal vv


  • A = clivus, petrous temporal bone
  • basilar (pontine) sulcus (ventral)
  • anterior cerebellopontine fibres -> middle cerebellar peduncle
  • dorsal/pontine tegmentum (post part pons containing reticular formation, nuclei of CNV-VIII)
  • cerebellopontine angle cisterns
  • superior medullary velum
  • contains reticular activating system

Vascular supply:

  • pontine branches of the basilar a
  • anterior pontomesencephalic v and lateral pontine vv


  • cerebral peduncles = crura cerebri (corticospinal tract) + tegmentum separated by substantia nigra
  • red nuclei and substantia nigra have ferritin deposition
  • tegmentum (ant to cerebral aqueduct) – contains fibre tracts, red nuclei, nuclei or CNIII and CNIV, periaqueductal grey matter
  • quadrigeminal/tectal plate (tectum) posterior to cerebral aqueduct (of Sylvius), contains quadrigeminal bodies = corpora quadrigemini
    • superior colliculi -> superior brachium -> lateral geniculate body (optic)
    • inferior colliculi -> inferior brachium -> medial geniculate body (auditory)

Vascular supply:

  • central branches of superior cerebellar a
  • posterior mesecephalic vv -> great cerebral v

Cranial Nerves

  • CN I (olfactory) – neurosensory cells roof of nasal cavities -> cribriform plate -> olfactory bulb -> olfactory tract.
  • CN II (optic) – optic canal (intraocular, intraorbital, intracanalicular and intracranial segments)
  • CN III (oculomotor) – nucleus in midbrain posterior to red nucleus adj to cerebral aqueduct (interconnects with CNIV-V via medial longitudinal fasciculus MLF for eye movements) -> exits anterior paramedian between peduncles -> between PCA and superior cerebellar aa -> lateral to PComm –> cavernous sinus –> superior orbital fissure. Supplies ciliary m, sphincter of pupil, extraoccular muslces (except LR and SO: LR6SO4), levator palpebrae.
  • CN IV (trochlear) – nucleus just below CN3 adj to aqueduct -> exits dorsal midbrain -> ant-inf between PCA and superior cerebellar -> cavernous sinus below CNIII -> superior orbital fissure. Supplies superior oblique.
  • CN V (trigeminal) – nuclei in pons (2), midbrain (mesencephalic nucleus) and medulla/cervical cord (spinal nucleus) -> exits ant-lat mid pons -> trigeminal/Gasserian/semilunar ganglion in Meckel’s cave. Supplies sensation to face, sinuses, teeth, muscles of mastication [V3];
    • V1 (opthalmic) -> inferior cavernous sinus -> superior orbital fissure. Supplies upper sensation to upper face, eye, lacrimal gland, nose.  Supraorbital, supratrochlear, infratrochlear, anterior ethmoidal nerves.
    • V2 (maxillary) -> foramen rotundum -> pterygopalatine fossa. Zygomatic nerve, infraorbital nerve (ingerior orbital fissure), superior alveolar branches, meningeal branches. Sensation maxillofacial region, upper teeth and gingiva, inferior eyelid, upper lip, nose.
    • V3 (mandibular) -> foramen ovale (meningeal branch -> foramen spinosum). Anterior branches supply masseter, temporalis, pterygoids, tensor tympani, tensor veli palatini, anterior belly of digastric, mylohyoid. Posterior branch divides into auriculotemporal, lingual (sensation and taste fibres anterior 2/3 tongue from chorda tympani) and inferior alveolar nerves (-> mandibular canal, supplying mylohyoid, anterior digastric, gingiva and mandibular teeth).
    • Aucirulotemporal nerve – connects V3 and CN7 behind mandible. During is course it surrounds middle meningeal artery.
  • CN VI (abducent) – nucleus mid pons -> exits at junction of pons and pyramids of medulla –> Dorello’s canal (dura over sphenoid) -> lateral cavernous sinus -> superior orbital fissure. Supplies lateral rectus.
  • CN VII (facial) – motor nucleus in midpons -> encircles abducens nucleus (forming facial colliculus) -> superior salivatory nucleus and nucleus solitarius -> exits lateral to CN VI superior to olives –> ant-sup internal acoustic meatus -> geniculate ganglion (greater superficial petrosal nerve supplying lacrimal apparatus) -> inferior (branches to stapedius, chorda tympani which joins lingual branch of V3) -> stylomastoid foramen -> lateral around retromandibular vein in parotid gland -> masticator space. Supplies muscles of facial expression.
    • nervus intermediatus (smaller sensory portion of nerve) -> internal acoustic meatus between CN VII and CN VIII. Supplies submandibular, sublingual, lacrimal glands, anterior 2/3 tongue, soft palate sensation.
  • CN VIII (vestibulocochlear/acoustic) – cochlear and vestibular nuclei in superior medulla -> exits pontomedullary junction superior to olives -> internal auditory canal (cochlear division ant-inf, vestibular branch post). Supplies cochlea and semicircular canals.
  • CN IX (glossopharyngeal) – nuclei in medulla -> exit in postolivary sulcus -> pars nervosa of jugular foramen. Supplies taste posterior 1/3 tongue, tonsils, pharynx, middle ear, stylopharyngeus, upper pharyngeal mm, parotid.
  • CN X (vagus) – nuclei in medulla (3) -> exits in postolivary sulcus -> pars vascularis of jugular foramen -> runs in carotid sheath. Supplies palate, pharynx, larynx, trachea, bronchi, lungs, heart, GI tract, external ear. Recurrent laryngeal nerves loop under aorta on L and SCA on R to supply all muscles of larynx except cricothyroids.
  • CN XI (spinal accessory) – roots of 1st 3 cervical nerve roots and motor nucleus in lower medulla –> ascends in ansa cervicalis (adj to carotid sheath) -> pars vascularis of jugular foramen. Supplies SCM, trapezius, infrahyoid strap muscles.
  • CN XII (hypoglossal) – nucleus in medulla -> exit in preolivary sulcus -> hypoglossal canal. Supplies intrinsic muscles of tongue, genioglossus, styloglossus, hyoglossus. Ansa cervicalis branches supply anterior strap muscles.


  • superior cerebellar peduncle = brachium conjunctivum
  • middle cerebellar peduncle = brachium pontis
  • inferior cerebellar peduncles = restiform body (inf-med to middle peduncle)
  • folia
  • arbour vitae (cerebellar white matter, ‘tree of life’)


  • A = 4th ventricle, pons, mastoid, petrous temporal bone
  • P = occipital bone
  • S = quadrigeminal plate cistern, pineal gland, tentorium
  • I = cisterna magna
  • lateral = sigmoid sinuses


  • paramedian sulcus
  • ligular (I, continuous with superior medullary velum)
  • central lobule (II&III)
  • culmen (IV&V)
  • primary fissure = fissure prima
  • declive (VI)
  • folium (VIIA)
  • horizontal fissure
  • tuber (VIIB)
  • pyramid (VIII)
  • uvula (IX)
  • posterolateral sulcus/fissure
  • nodule (X)


  • anterior lobe (small, sup)
    • quadrangular lobule
  • primary fissure
  • posterior lobe (large, inf)
    • simple lobule
    • superior (anseriform) and inferior (caudal) semilunar lobules (separated by horizontal fissure
    • biventer lobule
    • cerebellar tonsils
  • posterolateral sulcus
  • flocculonodular lobe (betw anterior and posterior lobes anteriorly)
  • flocculus

Deep Nuclei:

  • dentate nucleus (lat), may calcify in later life
  • emboliform, globose and fastigial nuclei (med)

Functional Anatomy and Pathways

  • commissural fibres (connect corresponding areas between hemispheres)
  • association/arcuate fibres (betw diff parts of same hemisphere)
  • projection fibres (cortex -> lower centres)
  • centrum semiovale = semioval centre (cerebral white matter)
  • corona radiata (internal capsule -> centrum semiovale; contains corticospinal, corticopontine, corticobulbar tracts)

Motor pathways:

  • Precentral (primary motor cortex) gyrus homunculus: lower limb sup-med along paracentral lobule (toes->trunk with hip at top of precentral sulcus and leg med), upper limb sup-lat (shoulder->thumb), neck, face (large esp tongue and mouth) inferior just above sylvian fissure (speech motor centre at frontal operculum), swallowing.
  • Pyramidal tract – voluntary movement, abnormality causes weakness, paralysis, spasticity.
    • Corticospinal tract: precentral gyrus –> corona radiata/centrum semiovale -> posterior limb of internal capsule -> central cerebral peduncle -> anterior pons -> pyramids of medulla -> most ducussate in pyramidal decussation -> lateral corticospinal tract of spinal cord. 15% don’t decussate in medulla -> anterior corticospinal tract in anterior funiculus (along anterior medial fissure of spinal cord). Fibres of the pyramidal tract (ant and lateral corticospinal tracts) synapse with anterior horn cells
    • Corticobulbar tract (face): precentral gyrus -> corona radiata -> genu of internal capsule -> anterior medial cerebral peduncle -> bilateral motor CN nuclei in brainstem, apart from lower face which is only contralateral
  • Extrapyramidal system regulates motion, with abnormality causing involuntary movements, tremor, chorieform (jerking), athetoid (slow sinuous), hemiballismic (flailing), rigidity . Interconnections of the corpus striatum (receives from cerebral cortex, thalamus, substantia nigra via internal and external capsule), dentate nuclei of cerebellum, red nucleus of midbrain
    • Rubrospinal tract (motor control of contralateral limb): red nucleus -> decussate in ventral tegmentum -> lateral funiculus of spinal cord -> post-lat white matter of cord.
    • Reticulospinal tract (automatic movements eg walking, stretching, orientating): pons and medulla -> ipsilateral anterior column of spinal cord
    • Vestibulospinal tract (balance, head and neck coordination): vestibular nuclei -> ipsilateral anterior column of spinal cord

Sensory pathways:

  • Postcentral (primary somatosensory) gyrus homunculus: genitals inf-med, lower limb sup-med (toes->trunk), upper limb sup-lat (shoulder->thumb), face, mouth, pharynx, intra-abdominal.
  • Spinothalamic tract (pain, temperature, some touch and pressure): peripheral nerves -> dorsal root ganglia, ascend 1-2 segments -> substantia gelatinosa of dorsal horn -> cross midline in anterior white commisure -> lateral spinothalamic tract -> spinal lemniscus (lat mid medulla, central pons, lateral midbrain) -> thalamus -> postcentral gyrus.
  • Posterior column-medial lemniscus tract (light touch, pressure): ipsilateral posterior column and contralateral anterior column -> nucleus proprius of dorsal horn -> anterior spinothalamic tracts -> medial lemniscus (lat to medial lemniscus) -> thalamus -> anterior internal capsule -> centrum semiovale -> postcentral gyrus.
  • Lateral lemniscus (proprioception, fine touch, vibration): posterior column (some fibres descend forming fire reflex arcs) -> fasciculus gracilis and fasciculus cuneatus -> gracile and cuneate nuclei in medulla -> ducussate -> medial lemniscus (post medulla and pons) -> thalamus -> internal capsule -> postcentral gyrus.

Visual pathway:

  • Rods and cones -> secondary sensory ganglion cells in retina -> optic nerve -> optic chiasm (temporal fibres/nasal field remain uncrossed, nasal fibres/temporal field decussate) -> optic tracts -> lateral geniculate body of thalamus (some ascend to CNIII nucleus for pupillary reflex, some to superior colliculus for tracking) -> geniculocalcarine tract (optic radiation) through posterior post limb internal capsule. Inferior radiation/sup field (Meyer’s loop fibres) pass around temporal horn -> lower lip calcarine fissure. Superior fibres through parietal lobe -> upper lip calcarine fissure. Macular -> ocipital pole over wider area
    • Wilbrand’s knee – some inferonasal fibers loop into contralateral optic nerve. Junctional syndrome – compression of one optic nerve may involve contralateral Wilbrand’s fibres (superotemporal vision)
  • Primary visual/striate calcarine cortex at medial occipital lobe
  • Blood supply:
    • lateral geniculate body – anterior choroidal a.
    • optic radiations – anterior choroidal, MCA, PCA
    • visual cortex – PCA, some of MCA

Auditory pathway:

  • Organ of Corti in cochlea -> cochlear division of CNVIII -> ant-inf internal auditory canal -> junction between pons and medulla -> dorsal and ventral cochlear nuclei in upper dorsal medulla -> some fibres decussate, trapezoid body in lateral lemnsicus of pons -> inferior colliculus -> medial geniculate nucleus of thalamus -> auditory radiation in posterior limb internal capsule -> primary auditory cortex in ant-sup transverse temporal and superior temporal gyri.

Olfactory pathway:

  • Ciliary nerves in upper nasal cavity -> olfactory bulb -> olfactory tracts -> olfactory trigone (ant to anterior perforated substance)
  • Lateral olfactory stria -> entorhinal cortex of uncus with efferents to amygdala
  • Medial olfactory stria -> septal area -> subcallosal gyrus

Gustatory pathway (taste):

  • Anterior 2/3 tongue -> chorda tympani (alongside V3) -> CNVII -> otic and geniculate ganglia -> nucleus solitarius.
  • Posterior 1/3 tongue -> CNIX -> petrosal ganglion -> nucleus solitarius.
  • Nucleus solitarius -> pons, thalamus (-> sensory cortex), hypothalamus, amygdala


  • Usually left hemisphere, some right or both (usually left-handed).
  • Broca’s motor speech area at frontal operculum. Abnormality causes expressive aphasia (difficulty to initiate speech, non-fluent).
  • Wernicke’s auditory association cortex at the posterior aspect of superior temporal gyrus – receptive understanding of speech. Abnormality causes sensory/receptive aphasia (fluent but incorrect language content eg word salad).
  • Arcuate fasciculus connects Broca’s and Wernecke’s areas. Abnormality causes conductive aphasia (intact comprehension and fluent speech production, but poor speech repetition).

Brodmann areas – functional units of cerebral hemispheres

  • 1,2,3 – Postcentral gyrus. Primary sensory cortex.
  • 4 – Precentral gyrus. Primary motor cortex.
  • 6 – Supplemental motor area (SMA). Planning of complex coordinated movements .
  • 7 – Parietal, posterior, to postcentral sensory cortex. Visual motor coordination.
  • 8 – Superior frontal gyrus, anterior to premotor cortex. Control of eye movements, planning of complex movements.
  • 9,10,46 – Dorsolataral prefrontal cortex. Executive functions.
  • 10,11,47 – Orbitofrontal cortex. Decision-making processes .
  • 17 – Posterior medial occipital. Primary visual cortex .
  • 22,42 – Posterior superior temporal. Wemicke’s speech recognition area (auditory association cortex).
  • 23,29,30,31 – Posterior cingulate. Memory, spatial awareness, proprioception .
  • 32,33 – Anterior cingulate. Coordination of cognitive functions of the frontal lobe with motor cortex, reward anticipation, motivation, decision making.
  • 39 – Inferior parietal lobule, angular gyrus. Word comprehension and arithmetic functions.
  • 40 – Inferior parietal lobule, supramarginal gyrus. Word recognition.
  • 41,42 – Superior mid lateral temporal. Primary auditory cortex.
  • 44,45 – Inferior lateral frontal lobe. Broca’s motor speech area.

Talairach and Tournoux space – mapping of the brain in relation to AC-PC line. X is positive on L, negative on R; Y positive anterior to AC-PC midline, negative post; Z positive above AC-PC line, negative below.

Ventricles and Cisterns

  • CSF 150mL = ventricles 25mL + around spinal cord 75mL + cortical sulci and cisterns 50mL. Intracranial fluid increases from ~75mL to 150mL (women) and 190mL (men) with age.
  • ependyma (lining of ventricles and choroid plexuses)
  • choroid plexuses (of blood vessels, calcifies ~5% <15yo, most by 40yo)
  • CSF made at 500mL/24hr or 0.4mL/min
  • CSF -> arachnoid villi (2/3), spinal villi or down nerve sheaths to perineural lymphatics

Lateral Ventricles

  • frontal/anterior horn (S = rostrum and genu, tapetum; I/lat = head caudate; medial = septum pellucidum)
  • interventricular foramen of Monro
  • body/atrium of the ventricle (med = fornix, choroidal fissure, thalamus; lateral = thalamostriate groove and vein, body caudate)
  • trigone of lateral ventricle
  • temporal/inferior horn (S = tail caudate, amygdyla; I = pes hippocampi, crura of fornix; lateral = tapetum)
  • occipital/posterior horn (I = collateral sulcus; medial = calcarine sulcus; lateral = tapetum, optic radiation)
  • calcar avis (involution of medial wall of posterior horn due to calcarine fissure)
  • septum pellucidum
  • laminae of the septum
  • choroid plexus (temporal horns -> inner body -> interventricular foramen -> 3rd ventricle; glomus = enlargement in lateral ventricles)
    • choroidal fissure (betw fornix and thalamus where choroid plexus is attached)
    • tela choroidea of lateral ventricles (double layered fold of pia and ependyma containing plexus)
    • anterior choroidal a (ICA -> anterior part of inferior horn)
    • posterior choroidal aa (PCA -> body, posterior part of inferior horn)
    • choroidal v (inf horn -> interventricular foramen -> internal cerebral v


  • cavum septi pellucidi (10%)
  • cavum vergae (post to interventricular foramen and columns of fornix, present at birth in 60%, closes by 2/12)
  • occipital horns may may be absent/large/assymetrical (usually L>R)

Third Ventricle (2-10mm width )

  • massa intermedia (non-neural connection in 60%)
  • supra-optic recess
  • infundibular recess
  • suprapineal recess
  • pineal recess
  • choroid plexus of 3rd ventricle (roof)
    • tela choroidea of 3rd ventricles = velum interpositum (triangular vascular pia mater at base of choroid plexus)
  • cerebral aqueduct (post 3rd -> superior 4th, 15 x 1-2mm)


  • A = lamina terminalis, optic chiasm
  • P = pineal gland
  • S = anterior commisure, columns of fornix, interventricular foramen, body of fornix, choroid plexus
  • I = subthalamic/hypothalamic groove, hypothalamus
  • lateral = thalamus

Fourth Ventricle

  • floor = rhomboid fossa, pons, medulla
  • roof = sup&inf cerebellar peduncles, sup&inf medullary velum
  • choroid plexus of 4th ventricle (inf medullary velum; inferior cerebellar a)
  • foramen of Magendie = median aperture (inf medullary velum -> cisterna magna)
  • lateral recesses
  • foramen of Luschka = lateral aperture (->pontine cistern)
  • central canal of spinal cord

Subarachnoid Cisterns

  • spinal subarachnoid space
  • cisterna magna = cerebellomedullary cistern (vertebral aa, PICA)
    • megacisterna magna (V)
  • cerebello-pontine angle cistern
  • superior vermian cistern
  • quadrigeminal plate cistern = cistern of the great cerebral vein (confluence of int cerebral vv and basal vv, vein of Galen)
  • ambient cistern (post cerebral a, basal v)
  • wings/lateral extensions of the ambient cistern = retropulvinar cistern (lat-sup around posterior thalamus)
  • cistern/cavum of the velum interpositum (sup to 3rd ventricle between layers of tela choroidea beneath splenium and fornix -> quadrigeminal plate cistern; internal cerebral vv)
  • pontine/prepontine cistern (basilar a, pontine and labyrinthine br)
  • interpeduncular/intercrural cistern (post COW)
  • suprasellar cistern (->lat to sylvian cistern; chiasmatic cistern = part anterior to optic chiasm; anterior COW)
  • cistern of the lamina terminalis (ant to lamina terminalis and anterior commisure)
  • pericallosal cistern = cistern of corpus callosum (ACA)

Intracranial Arteries

Internal Carotid Artery (ICA)

  • C3-5->circle of Willis
  • 6 bends before terminal division
  • carotid siphon (U-shaped loop; cavernous + supraclinoid portions)

cervical segment (->carotid canal):

  • tonsillar loop
  • no branches
  • A/med = thyroid, trachea
  • P = sympathetic trunk, prevertebral mm, transverse processes C1-3
  • medial = ECA, pharynx
  • lateral = vagus n, IJV, parotid, styloid process and mm

petrous segment (->foramen lacerum) in the carotid canal (thin bone separating from middle/inner ear), surrounded by sympathetic plexus.

  • caroticotympanic artery (-> tympanic membrane)
  • vidian/pterygoid artery (-> anast with recurrent br of greater palatine a)

cavernous segment (->ophthalmic a):

  • cavernous artery (->walls of cavernous sinus, dura)
  • meningohypophyseal trunk (->dorsal meningeal and inferior hypohyseal aa [->post lobe pit gland])
  • inferolateral trunk (->tentorium, anast with branch of ophthalmic a, supply V3, anast with acc meningeal a)
  • S = diaphgrama sella
  • I/lat = CNVI
  • lateral = CNIII,IV,V1,V2
  • medial = sella turcica

supraclinoid segment (after piecing dura):

  • ophthalmic artery (inf/lat to optic n in optic foramen ->sup -> medial wall of orbit)
  • superior hypophyseal artery (->hypothalamus)
  • posterior communicating artery (PComm)
  • anterior choroidal artery
    • 1st/cisternal part (->plexal/choroidal point at choroidal fissure, anterior tip of inferior horn lateral ventricle) ->crus cerebri, lateral geniculate body
    • 2nd/plexal part -> choroid plexuses, posterior limb internal capsule, basal ganglia, hippocampus
  • striate arteries (->lentiform, caudate nuclei, internal capsule)
  • anterior and middle cerebral arteries
  • I = dura, arachnoid
  • medial = optic chiasm
  • lateral = anterior clinoid process


  • persistent trigeminal artery (petrous/cavernous ICA -> upper basilar a)
  • persistent pre-atlantal a (ICA/ECA -> vertebral a at level of C2)
  • persistent otic a (petrous ICA -> proximal basilar a via internal auditory canal)
  • persistent hypoglossal a (cervical ICA -> proximal basilar a via hypoglossal canal)
  • aberrant carotid artery (into tympanic cavity)
  • tortuous cervical ICA
  • high CCA bifurcation
  • ophthalmic a from supraclinoid (83%), cavernous (7.5%) or distal supraclinoid (6.5%) segments

Anterior Cerebral Artery (ACA)

anterior perforated substance -> cistern of the lamina terminalis -> interhemispheric fissure

  • A1 segment (->AComm):
    • anteromedial lenticulostriate/central perforating arteries
    • anterior communicating a (AComm, -> small perforating branches)
  • A2 segment (->bifurcation):
    • Heubner’s recurrent a = medial striate artery (->caudate, lentiform nuclei, anterior limb internal capsule)
    • orbitofrontal/medial frontobasal artery (->inf frontal lobe, gyrus rectus)
    • frontopolar/polar frontal artery (->ant pole)
  • A3 segment = pericallosal artery:
    • callosomarginal artery (->ant, mid and posterior internal/medial frontal branches, paracentral a)
    • central branches (->corpus callosum, septum pellucidum, anterior lentiform nucleus, head caudate)
    • superior and inferior internal parietal aa
    • precuneal artery (marginal sulcus)

Middle Cerebral Artery (MCA)

  • M1/sphenoidal/horizontal segment of MCA
    • lenticulostriate/anterolateral central arteries (->artery of cerebral haemorrhage; ->head caudate, putamen, lateral 1/3 globus pallidus, superior 1/2 anterior limb, genu internal capsule)
    • A = sphenoid ridge
    • P = brainstem, PComm
    • S = petrosal sinus, optic chiasm, olfactory tracts, anterior perforated substance, int&ext capsule
    • I = sphenoid, temporal bone
    • medial = pituitary, mamillary bodies, ICA, cavernous sinus, optic chiasm
    • lateral = temporal lobes, sylvian fissure
  • M2/insular segment(s) of MCA
  • M3/opercular segments of MCA
  • M4/terminal segments of MCA
    • sylvian triangle (sharp angulation of opercular segment branches)
    • sylvian point/genu (most superior point of aa in sylvian fissure)

Anterior/superior group branches:

  • orbitofrontal/lateral frontobasal artery
  • prefrontal sulcal artery = operculofrontal/candelabra group arteries
  • precentral/pre-rolandic sulcal artery
  • central/rolandic sulcus artery

Posterior/inferior groups branches:

  • anterior parietal/postcentral sulcal artery
  • posterior parietal artery
  • angular artery (in angular gyrus)
  • anterior, middle and posterior temporal arteries


  • bifurcation (50%) and trifurcation (25%) of M2 or distal M1 (V) with superior, middle (V) and inferior branches of MCA
  • anterior choroidal a from MCA
  • duplicated MCA
  • fenestrated M1

Vertebral Artery

L>R in 80%

  • 1st/prevertebral part (SCA->C6 foramen transversarium)
    • A = vertebral v, inferior thyroid a, thoracic duct, carotid sheath (CCA,IJV,vagus), scalenus anterior
    • P = transverse process C7, ventral rami C7/8, longus colli
    • medial = sympathetic ganglia
    • lateral = thyrocervical a, inferior thyroid a crossing ant
  • 2nd/cervical/intraforaminal part (->C2 foramen transversarium)
    • surr = vertebral venous plexus
    • P = spinal nn
    • medial = vertebral lateral masses
    • spinal/radicular branches -> spinal canal
    • muscular branches -> deep neck muscles, anast with occipital and ascending pharyngeal aa
  • 3rd/atlantic part (->dura of vertebral canal)
    • A = atlas superior articular process
    • medial = spinal cord
    • I = posterior arch atlas, C1 nerve root
  • 4th/intracranial part (->basilar artery)
    • A = clivus
    • P = medulla, denticulate ligament
    • medial = anterior spinal a
    • superior = basiocciput
    • branches to medulla oblongata
    • anterior spinal arteries
    • posterior spinal arteries
    • posterior inferior cerebellar a (PICA) with ant, lateral and posterior medullary segments. Size inversely proportional to AICA
      • anterior and posterior meningeal aa
      • choroidal branch to 4th ventricle
      • tonsillohemispheric a branch
      • inferior vermian a/medial branch


  • L vertebral arising from aortic arch (betw L CCA and L SCA or distal to L SCA), L CCA or L ECA
  • R vertebral arising from R CCA
  • hypoplastic/absent right vertebral a
  • persistent foetal proatlantal intersegmental artery (ICA/ECA > foramen magnum > vertebral a)
  • bifid vertebral artery origin
  • posterior spinal from PICA
  • vertebral a entering transverse process C4-7
  • fenestration of the vertebral artery

Basilar Artery

pontomedullary junction -> PCA, in pontine cistern close to midline contralateral to dominant vertebral a

  • anterior inferior cerebellar artery (AICA; lateral and medial branches;- > ant&lat inferior cerebellum)
    • labyrinthine/internal acoustic artery (-> IAM)
  • pontine arteries
  • superior cerebellar artery (SCA) -> pons, superior cerebellar peduncle, inferior colliculus, superior vermian a (anast with inferior vermian a)
  • A = clivus, sphenoid sinus
  • P = pons
  • S = cerebral peduncles, posterior perforated substance
  • lateral = cranial nerves IV to VIII


  • labyrinthine or PICA from AICA

Posterior Cereral Artery (PCA)

  • P/med = cerebral peduncles
  • S = thalamus
  • I = tentorium, superior cerebellar a

P1 = pre-communicating segment (->Pcomm):

  • branches to cerebral peduncle, posterior thalamus, medial geniculate body, quadrigeminal plate
  • thalamostriate/posteromedial central perforating arteries (->post perforated substance -> thalamus and lentiform nucleus)

P2 = ambient segment:

  • inferior (anterior, middle and posterior) temporal branches
  • medial and lateral posterior choroidal arteries (-> around lateral geniculate bodies [supplying these] -> posterior part inferior horn lateral ventricle -> choroid plexus)

P3 = quadrigeminal segment:

  • internal occipital branch -> posterior pericallosal a and parieto-occipital a

P4 = calcarine branch

Circle of Willis

  • A = frontal lobe, olfactory tracts
  • P = pons
  • S = hypothalamus
  • I = sella turcica
  • medial = optic tracts, chiasm and nerves, pituitary stalk, mamillary bodies
  • lateral = uncinate process

Variants of structure:

  • complete in 90%, variations in 60%
  • unilateral or bilateral fetal type (33%; hypoplasia/absent P1, large PComm[=fetal PComm])
  • hypolastic (30%)/absent A1
  • hypoplastic (22%)/absent PComm
  • hypoplastic (3%)/absent/duplication AComm
  • hypoplasia/absent ICA
  • infundibular dilatation of basilar artery tip = basilar tip vestibule

Variants of branching:

  • azygous artery (single trunk ACA)
  • fusion of the ACA over a short distance, or A2s from a common trunk
  • artery of Percheron (single posteromedial central perforating aa -> medial thalami)
  • Heubner’s recurrent artery from A1 or M1 (instead of A2)
  • medial artery of the corpus callosum from AComm
  • double MCAs from ICA

Arterial Anastomoses

  • right -> left (AComm, PComm, vertebral aa, ant. spinal a.)
  • ICA -> vertebral (PComm)
  • ICA -> ECA (ophthalmic -> supraorbital/supratrochlear/dorsal nasal -> angular -> facial)
  • ICA -> ECA (ophthlamic -> supraorbital/palpebral aa -> superficial temporal a)
  • ICA -> ECA (ophthalmic -> br of middle meningeal a [in superior orbital fissure])
  • ICA -> ECA (vidian a -> greater palatine a -> maxillary a)
  • ICA -> ECA (caroticotympanic -> anterior tympanic -> maxillary a)
  • ECA -> SCA (ascending pharyngeal -> ascending cervical -> inferior thyroid -> thyrocervical trunk)
  • ECA -> SCA (occipital -> deep cervical -> costocervical trunk)
  • vertebral -> SCA/ECA (anterior spinal of vertebral aa -> spinal segmental medullary -> deep or ascending cervical, ascending pharyngeal)

Intracranial Veins

no intracerebral venous valves

Dural Venous Sinuses

between layers of dura

Superior group receive from diploic v (skull), anast with scalp and face via emissary vv. Arachnoid granulations and villi project into venous lakes that are lateral projections of the superior sagital sinus

  • superior sagittal sinus (<- cortical veins = superior cerebral veins) -> right transverse sinus (usually)
  • bifurcation of the superior sagittal sinus (V)
  • inferior sagittal sinus -> venous confluence (of vein of Galen and inferior sag sinus) -> straight sinus -> left transverse sinus
  • torcular herophili = confluence of sinuses (at internal occipital protuberance)
  • occipital sinus (-> torcula)
  • lateral sinus = transverse + sigmoid sinuses
  • jugular bulb (dilatation in foramen magnum)
  • high jugular bulb (V, into hypotympanum)
  • ‘cavernous nodules’ = pseudo-erosive changes of bone

Basal group:

  • superior and inferior ophthalmic veins
  • sphenoparietal sinus (along sphenoid ridge)
  • cavernous sinus (ophthalmic v, sphenoparietal sinus, superficial middle cerebral v -> petrosal sinuses)
    • medial = pituitary gland, body of sphenoid; S = supraclinoid carotid a, optic tract
    • central carotid a lateral wall S->I CNIII,IV,V1, V2, CNVI; sympathetic cavernous plexus (->eye)
  • anterior and posterior intercavernous sinuses (one/both may be absent [V])
  • superior petrosal sinus (cavernous -> along petrous ridge -> sigmoid sinus)
  • basilar venous plexus
  • inferior petrosal sinus (cavernous -> IJV)

Superficial Cerebral Veins

  • flow centrifugally
  • superficial middle cerebral vein = Sylvian vein -> sphenoparietal sinus -> cavernous sinus
  • vein of Trolard = superior anastomotic vein (superficial MCV -> superior sagittal sinus)
  • vein of Labbe = inferior anastomotic vein (superficial MCV -> transverse sinus)

Deep Cerebral Veins

  • flow centripetally
  • septal vein = anterior v of septum pellucidum (-> int cerebral v)
  • thalamostriate vein (thalamostriate groove [betw thalamus and lentiform] -> internal cerebral v)
  • choroid vein (choroid plexus lateral ventricle -> internal cerebral v)
  • internal cerebral vv (at venous angle [post foramen of Monro]; between layers of tela choroidea roof of 3rd ventricle) -> vein of Galen = great cerebral vein (inf to splenium)
  • deep middle cerebral vein + anterior cerebral vein + striate v )<- inferior basal ganglia via anterior perforated substance) -> basal vein of Rosenthal -> vein of Galen

Veins of the Posterior Fossa

Superior group:

  • posterior mesencephalic vein (around upper midbrain) -> vein of Galen
  • precentral cerebellar vein (ant) + superior vermian vein (post) -> superior cerebellar v -> vein of Galen

Anterior group:

  • anterior pontomesencephalic vein -> basal vein of Rosenthal
  • lateral pontine vv -> petrosal vein of Dandy (ant to pons; ->superior petrosal sinus) and posterior mesencephalic vein (superiorly)
  • inferior medullary vv -> spinal vv

Posterior group:

  • inferior vermian vein -> straight sinus/torcular herophili

Glymphatic System

There is no dedicated lymphatic system in the CNS, except for in the meninges. Hypotheses for clearance of waste products in the brain include glymphatic system, IPAD. The driving force behind both systems is arterial pulsation.

Glymphatics – CSF migrates into arterial perivascular spaces (through layer of pia) in the direction of blood flow. Fluid passes through glial footplate aquaporin 4 channels or between footplates into brain interstitium. Migration of fluid into venous perivascular spaces, with some fluid ?extending into venous lumen, rest passing back into CSF. CSF may drain into meningeal lymphatic channels in the region of olfactory apparatus (~50%) or near dural venous sinuses, then passing to upper cervical lymph nodes. Some CSF also drains into venous system via arachnoid villi.

Function of glymphatic system reduces with age, reduced sleep, reduced physical activity, prone vs supine position, high alcohol intake (improves with low intake), traumatic brain injury, subarachnoid haemorrhage, infection. May be implicated in pathogenesis of Alzheimer disease, glaucoma, NPH, Meniere’s.

IPAD (intramural periarterial drainage) – CSF migrating into arterial perivascular spaces may then extend into arterial wall. Fluid then migrates in direction opposite to blood flow to upper cervical lymph nodes.

IPAD function is impaired with age, amyloid deposition in vessels, arterial pulsatility.