Alternate set of notes

• Rostral


  Towards head end
• Caudal


  Towards tail end
• Membranous coverings of the brain and spinal cord


  • Protection
  • Supporting framework for vessels + venous sinuses
  • Enclose the subarachnoid space
• Dura Mater (aka pachymeninx)


  • 2 layers: external periosteal layer & inner meningeal layer
  • Mostly adherent to each other except where they enclose the dural venous sinuses
  • External periosteal layer ain't in the spinal cord
• Dural infoldings (reflections) of meningeal layer form partitions in cranial cavity


  1. Falx cerebri

  2. Tentorium cerebelli

  3. Falx cerebelli

  4. Diaphragma sellae

  
• Falx cerebri


  • Lies in longitudinal fissure; free border lies above corpus callosum
  • Continuous post.ly with tentorium cerebelli
• Tentorium cerebelli


  • Lies in transverse cerebral fissure
  • Separates occipital lobe from cerebellum
  • Tentorial notch: free border (anteromedially) through which brainstem extends from post. To middle cranial fossa

  
• Falx cerebelli


  • Vertical infolding inferior to falx cerebri, attaches to internal occipital crest
  • Separates cerebellar hemispheres

  
• Diaphragma sellae


  • Circular sheet of dura suspended between clinoid processes, forming a roof over sphenoid's hypophysial fossa
  • Covers pituitary gland; has aperture for hypophysial veins & infundibulum
• Arteries supplying the dura


  • Middle meningeal a. (branch of maxillary a.)
  • Meningeal branch of ophthalmic arteries
  • Branches of occipital arteries
  • Branches of vertebral arteries

  
• Nerve supply to the dura


  • Meningeal branches from CNV: Ant. Meningeal branches of ethmoidal nerve (CNV1), Meningeal branches of maxillary (CNV2) and Mandibular (CNV3) – dura of ant. & middle cranial fossa
  • Tentorial nerve (branch of CNV1 ophthalmic n.) – post. Cranial fossa
  • Upper cervical nerves
• Arachnoid mater


  • Thin avascular membrane
  • Attaches to dura by several layers of flattened cells
  • Conforms to general shape of brain/doesn't dip into sulci
  • Separated from pia by arachnoid trabeculae and subarachnoid space for circulation of cerebrospinal fluid (CSF)
• Arachnoid trabeculae


  • Strands of collagenous connective tissue from arachnoid to pia
  • Maintain patency
• Arachnoid villi/granulations


  • Evaginations (outgrowths) of arachnoid projecting through dura into sinuses
  • With age become large & aggregated (granulations)
• Pia mater


  • Highly vascular
  • A delicate membrane - 2 to 3 cells thick
  • Attaches to end feet of arachnoid trabeculae
  • Invests surfaces of brain and closely follows all sulci/surfaces of brain
  • Arteries and veins penetrate the pia when they enter/leave brain substance (perivascular space)
• Spinal meninges


  • Devoid of fibrous layer of dura which ends at margin of foramen magnum
  • Not much difference in arachnoid mater
  • Spinal pia mater forms 21 denticulate ligaments and thickened anteriorly to give a shining appearance in midline, called linea splendens

  
• Lateral Ventricles (1st & 2nd)


  • Located within the cerebral hemispheres
  • Parts: Anterior (Frontal) horn, Body, Posterior (Occipital), Inferior (Temporal)
  • Opens through interventricular foramen into 3rd ventricle

  
• 3rd ventricle


  • Located between right & left halves of diencephalon
  • Lateral walls formed by thalamus and hypothalamus on either side
  • Roof formed by pia-epyndyma spanning between stria medullaris thalami nerve bundles
  • Interventricular foramen (Monro): Aperture in rostral 3rd venricle, between column of fornix & ant. pole of thalamus
  • Continuous posto-inferiorly with cerebral aqueduct, connecting it to 4th ventricle
• 4th ventricle


  • Diamond shaped
  • Floor: dorsal surface of brainstem beneath cerebellum
  • Roof: formed mostly by cerebellum except at caudal part which consists of pia + epyndyma, and rostral part which is partly formed by superior cerebellar peduncles bridged by superior medullary velum
  • CSF enters subarachnoid space via lateral & median apertures

  
• Lateral aperture (foramen of Lushka)


  Continuous with subarachnoid space of cerebellopontine angle

  
• Median aperture (foramen of Magendie)


  Opening in caudal roof, communicates between lumen of ventricle and cisterna magna
• Extradural Space/Epidural Space


  Potential/unnatural/pathological space at dura-cranial interface
• Subdural Space


  Potential/unnatural/pathological space at dura-arachnoid interface
• Subarachnoid/Leptomeningeal Space


  Real/naturally occurring space between arachnoid and pia, contains Cerebrospinal fluid (CSF), blood vessels and trabeculae cells
• Cisterna magna (aka cerebromedullary cistern)


  Dilation of subarachnoid space between cerebellum and dorsal surface of medulla, gets CSF from 4th ventricle's apertures
• Interpeduncular cistern


  Located at base of brain between temporal lobe, deepest between cerebral peduncles of midbrain, contains optic chiasm + circle of Willis, has subdivisions: Pre- and post- chiasmatic, Cistern of lamina terminalis, Supracallosal cistern

  
• Cistern ambiens (aka superior cistern)


  Between splenium (post. Part) of corpus callosum and superior surface of cerebellum, contains great cerebral vein and pineal gland

  
• Pontine cistern


  Basilar artery runs through it
• Cerebrospinal Fluid (CSF)


  • Colourless fluid in ventricles and subarachnoid spaces bathing brain and spinal cord
  • Volume: 150 ml
  • Manufactured at a rate of ~ 0.35 ml/ min (500 ml of total CSF made per day and replaced every 4-6 hours)
  • Functions: Supports and cushions brain/spinal cord, acts as buoyant fluid, maintains uniform pressure, provides nutrition and removes waste
• CSF circulation & reabsorption


  Most CSF produced by choroid plexus of lateral ventricle, flows through ventricles to subarachnoid space, majority flows superiorly round cerebral hemispheres to sites of reabsorption in dural venous sinuses via arachnoid villi

  
• Hydrocephalus


  • Excess accumulation of CSF which produces an elevated intracranial pressure and in infants can cause swelling of the ventricles
  • Also known as 'Water in the brain'
  • Could be Congenital or Acquired, caused by overproduction, obstruction, or problems with absorption of CSF
• Lumbar puncture (Spinal Tap)


  Withdrawal of CSF from lumbar cistern, based on absence of spinal cord below L2 with large space to S2, preferred site is between L3 & L4 or L4 & L5
• The cerebellomedullary cistern may be used to obtain a specimen of CSF when a lumbar puncture is not possible or unsuccessful
• Internal carotid artery


  • Origin: bifurcation of common carotid artery
  • Course: Enters middle fossa, bends as carotid syphon, passes through cavernous sinus, reaches surface of brain lateral to optic chiasm

  
• Extracerebral Branches of Internal Carotid Artery


  • Petrous part: Caroticotympanic branch, Pterygoid artery
  • Cavernous part: Cavernous brs, Meningeal brs, Hypophysial brs
  • After cavernous course: Ophthalmic

  
• Pre-terminal branches of Internal Carotid Artery

  Hypophyseal arteries, Ophthalmic artery, Anterior choroidal artery, Posterior communicating artery

  
• Anterior cerebral artery


  • Courses medially above optic nerve, passes into great longitudinal fissure, joined to opposite side by anterior communicating artery
  • Supplies medial surface & marginal area of superolateral surfaces of cerebrum

  
• Middle cerebral artery


  Largest cerebral artery, with most extensive cortical distribution

  
• Anterior cerebral artery


  • Courses medially above the optic nerve and then passes into the great longitudinal fissure, between the frontal lobes of the cerebral hemispheres
  • Joined to the corresponding vessel of the opposite side by the short anterior communicating artery
  • Within the great longitudinal fissure, the anterior cerebral artery follows the dorsal curvature of the corpus callosum, branches ramifying over the medial surface of the frontal and parietal lobes, which it supplies

  
• Cortical branches of anterior cerebral artery


  • Supply medial surface & marginal area of superolateral surfaces of cerebrum (includes the motor and sensory cortices for the lower limb + narrow lateral band of frontal and parietal cortices via fine terminal branches also extending out of the great longitudinal fissure)