Spinal Tract Anatomy and Cranial Nerves

eesohbel's version from 2015-08-03 20:36


Question Answer
Ventricle pathwaylateral-->3rd via foramen of monro--> cerebral aqueduct-->4th-->SA space via Luschka (lateral) and Magendie (medial)
Normal pressure hydrocephaluswacky/wobbly/wet
NO increase in SA space volume, expansion of ventricles disrupts fibers of corona radiata → dementia, ataxia, urinary incontinence
Communicating hydrocephalusless CSF absorption by arachnoid granulations → increased icp → papilledema and herniation
Hydrocephalus ex vacuoincreased CSF in atrophy (Alzheimers, advanced HIV, picks), ICP is normal and triad not seen
Noncommunicating hydrocephalusStructural blockage (stenosis of aqueduct of sylvius)

Spinal nerves and tracts

Question Answer
# of spinal nerves31 - 8cerv, 12 thoracic, 5 lumbar, 1 coccygeal
Vertebral disc herniationnucleus pulposus (soft central disc) herniates through anulus fibrosus (outer ring)
usually posterolaterally at L4-L5 or L5-S1
Spinal cord extends to where?L1-L2
Subarachnoid space extends to where?Lower border of S2
Lumbar tap levelsL3-L5
Conus medullaris syndromelesions at L2 leads to flaccid paralysis
Cauda Equinadamage to S2 to S4 leads to loss of contraction of anal sphincter.
Orientation of lateral coricospinal tractlegs are lateral
Orientation of dorsal columnsArms are lateral (fasciculus cuneatus)
Legs are medial (fasciculus gracilis)
Fn of dorsal column (ML pathway)ascending pressure, vibration, fine touch, proprioception
Decussation dorsal columnmedulla → ascends contralaterally in medial lemniscus
Fn of lateral spinothalamic tractpain/temp
Fn of anterior spinothalamic tractcrude touch, pressure
Decussation spinothalamic tractanterior white commissure → ascends contralaterally
Fn of lateral corticospinal tractDescending voluntary movement of contralateral limbs
Decussation of lateral corticospinal tractat caudal medulla descends contralaterally
UMN lesioneverything up (tone, DTRs, toes)
spastic paralysis
LMN lesioneverything down (muscle mass, muscle tone, reflexes, toes)
Flaccid paralysis
If corticospinal lesion above pyramidal decussation (caudal medulla)contralateral UMN less
If corticospinal lesion below pyramidal decussation (caudal medulla)ipsilaterlal UMN signs]
LMNventral horn


Question Answer
clasp knife spasticityUMN
spastic paralysisUMN
flaccid paralysisLMN

Spinal cord lesions

Area of destructionCharacteristics
Polio and Werdnig Hoffmag diseases. Anterior horns. LMN lesions only due to destruction of anterior horn. flaccid paralysis
MS-loss of white mater cervical region, random and asymmetric lesions
Charcot's triad
scanning speech
intention tremor
Lateral corticospinal degeneration and Anterior Horn degenerationALS-lateral corticospinal degeneration (UMN signs) and anterior motor horn degeneration (LMN signs)
Caused by defect in superoxide dismutase 1
Fasciculations with eventual atrophy
Tx with Riluzole (modest ↑ in survival with ↓ presynaptic glutamate release)
occlusion of anterior spinal artery-loss of everything but dorsal column's and lissauer's tract
perserved mechanosensation (dorsal column) and lissauer tract
Tabes dorsalis-loss of dorsal columns
Caused by 3° syphilis
Impaired sensation/proprioception and progressive sensory ataxia (no DTRs and positive Romberg)
Assoc w. Charcot's joints, shooting pain, Argyll Robertson pupils (small, bilateral pupils that accomodate but don't react)
syrinogmyelia-Anterior white commissure of spinothalamic tract (2nd order neurons)
bilateral loss of pain/temp (usually C8-T1)
Seen with Chiari 1 malformation
B12 or vitamin E-Demyelination of dorsal columns, lateral corticospinal tracts, and spinocerebellar tracts
ataxic gait
impaired position and vibration sense
difference between B12 presentation and vitamin EB12 will present with macrocytic anemia vitamin E will present w hemolytic anemia


Question Answer
spread of poliovirus in the bodyreplicates in oropharynx and small intestine, spreads via bloodstream to CNS
signs of poliovirus infectionmalaise, headache, fever, nausea
symptoms of poliomyelitisLMN signs (destruction of cells in anterior horn of spinal cord)
poliovirus can be recovered fromstool and throat
CSF findings in poliomyelitisincreased WBCs and slight protein elevation, no change in glucose
Werdnig-Hoffman disease iscongenital degeneration of anterior horns -> LMN lesion. floppy baby with tongue fasciculations.
inheritance of Werdnig-Hoffmanautosomal recessive
infantile Werdnig-Hoffman median age of death7 months
Friedreich's ataxia geneticsautosomal recessive GAA trinucleotide repeat
defect Friedreich's ataxiafrataxin; leads to impairment of mitochondrial function
findings in Friedreich's ataxiastaggering gate, frequent falling, nystagmus, dysarthria, pes cavus, hammer toes
Friedreichs ataxia presents in childhood withkyphoscoliosis
cause of death in Friedreich's ataxiahypertrophic cardiomyopathy
symptoms Horner's syndromeptosis, miosis, anhydrosis
oculosympathetic pathwayhypothalamus, intermediolateral column in spinal cord, superior cervical ganglion, to eye area
Brown Sequard at level of lesionloss of all sensation
spinal cord lesion in Brown Sequardhemisection of spinal cord
ipsilateral lesion in Brown SequardUMN signs below lesion. Ipsilateral loss of tactile, vibration and propioception sense below lesion.
contralateral lesion in Brown Sequardcontralateral pain and temperature (spinothalamic decussates at anterior white commisure.
Horner in Brown Sequardif lesion above T1

Landmark Dermatomes & reflexes

Question Answer
primitive reflexes normally disappear within 1st year of life, inhibited byfrontal lobe; frontal lobe lesion may cause reemergence of primitive reflexes
moro reflexabduct/extend limbs when startled, then draw together
rooting reflexmovement of head toward one side if cheek or mouth stroked (nipple seeking)
sucking reflexsucking response when roof of mouth is touched
palmar reflexcurling of fingers if palm is stroked
gallant reflextrekking one side of spine while newborn face down causes lateral flexion of lower body toward stimulated side

Clinical Reflexes

Question Answer
S1, S2"buckle my shoe" (Achilles reflex)
L3, L4"kick the door" (patellar reflex)
C5, C6"pick up sticks: (biceps reflex)
C7, C8"lay them straight" (triceps reflex)
L1, L2"testicles move" (cremaster reflex)
S3, S4"winks galore"


Question Answer
CNs that lie medially at brainstemIII, IV, VI, XII (factors of 12 except 1 and 2)
pineal glandmelatonin secretion, circadian rhythms
superior colliculiconjugate vertical gaze center
inferior colliculiauditory
parinaud syndromeparalysis of conjugate vertical gaze due to lesion in superior colliculi (e.g., pinealoma)
CN Ismell, only CN without thalamic relay
CN IIsight
pupillary constriction (sphincter pupillae; Edinger-Westphal nucleus, muscarinic receptors)
eyelid opening (levator palpebrae)
CN Vmastication, facial sensation, somatosensation from anterior 2/3 of tongue
CN VIIfacial movement
taste from anterior 2/3 tongue
salivation (submandibular and sublingual)
eyelid closing (orbicular oculi)
stapedius muscle in ear
CN VIIIhearing, balance
CN IXtaste and somatosensation from posterior 1/3 of tongue
salivation (parotid)
carotid body and sinus
CN Xtaste from epiglottic region
palate elevation
midline uvula
thoracoabdominal viscera
aortic arch chemo and baroreceptors
CN XISCM, trapezius
CN XIItongue movement
midbrain nucleiIII, IV
Pons nucleiV, VI, VII, VIII
medulla nucleiIX, X, XII
spinal cord nucleiXI
corneal reflexafferent is V1 nasociliary branch; efferent is VII temporal branch (orbicularis occuli)
lacrimationafferent V1 (loss of reflex does not preclude emotional tears); efferent VII
jaw jerkafferent V3 muscle spindle from masseter; efferent V3 to masseter
pupillaryafferent II, efferent III
gagafferent IX, efferent X
nucleus solitarius informationvisceral sensory, e.g., tate, baroreceptors, gut distention
nucleus solitarius CNsVII, IX, X
nucleus ambiguus infomotor innervation of pharynx, larynx, upper esophagus
nucleus ambiguus CNsIX, X
dorsal motor nucleus infoparasympathetic fibers to heart, lungs, upper GI
dorsal motor nucleus CNsX
LR6SO4lateral rectus CNVI, superior oblique CNIV

CN pathways

Question Answer
cribriform plateCN I
middle cranial fossa through sphenoid boneCN II-VI
optic canalCN II, ophthalmic artery, central retinal vein
superior orbital fissureIII, IV, V1, VI, ophthalmic vein, sympathetic fibers
foramen rotundumV2
foramen ovaleCN V3
foramen spinosummiddle meningeal artery
posterior cranial fossa through temporal or occipital boneVII-XII
internal auditory meatusVII, VIII
jugular foramenIX, X, XI, jugular vein
hypoglossal canalXII
foramen magnumspinal roots of XI, brain stem, vertebral arteries
passage of blood through venous sinusblood from eye and superficial cortex -> cavernous sinus -> internal jugular
things that run through cavernous sinusII, IV, V1, V2, VI, postganglionic sympathetics, internal carotid
cavernous sinus syndromeophthalmoplegia and decreased corneal and maxillary sensation, normal vision

Common CN lesions

Question Answer
CN V motor lesionjaw juts toward lesion (unopposed force of opposite pterygoid)
CN X lesionuvula deviates away from lesion (weak side collapses)
CN XI lesionweakness turning head to contralateral side (SCM), shoulder droop on ipsilateral side (trapezius)
CN XII lesion (LMN)tongue deviates toward lesion (lick your wound)

Cranial nerves

Question Answer
CN nuclei V, VI, VII, VIIIPons
CN nuclei IX, X, XIIMedulla
CN nuclei XISpinal Cord
CN nuclei III, IVMidbrain
CN nuclei I, IIForebrain
Cribiform plateCN I
Unilateral Optive Nerve LesionNo vision in ipsilateral eye
Lesion of Optic ChiasmLoss of temporal vision in both eyes (bitemporal hemianopsia)
Lesion of Optic TractLoss of vision in contralateral visual field in both eyes (homonymous hemianopsia)
Macular degenerationLoss of vision in center of both eyes
PCA infarction (MCA spared)Loss of vision in contralateral visual field (Homonymous hemianopsia) with macular sparing
Superior orbital fissureCN III
Superior orbital fissureCN IV
Superior orbital fissureCN VI
Eye looks up when adducted CN IV lesion
Eye deviates mediallyCN VI lesion
Eye deviates down and out (lateral strabismus)CN III lesion
Pupil dilationCN III lesion
PtosisCN III lesion
Afferent pupillary defect CN II
Efferent pupillary defect CN III lesion
Afferent pupillary defectShine light in one eye,neither pupil constricts "Marcus Gunn Pupil"
Efferent pupillary defect Pupil will not constrict when light shown in contralateral eye
Mass lesion of CN III more likely to compressParasympathetic fibers
Ischemic lesion of CN III more likely to affectMotor output to EOM
Superior orbital fissureOpthalmic branch of CN V
Foramen rotundumMaxillary branch of CN V
Foramen ovaleMandibular branch of CN V
Corneal reflexCN V + VII
Closes jawTemporalis, Masseter, Medial pterygoid
Opens jawLateral pterygoid
Which nerves run through cavernous sinusCN III, IV, VI, V1 and V2
Which nerves run through the Internal acoustic meatusCN VII, CN VIII
Lacrimal glandCN VII
Submandibular glandCN VII
Sublingual glandCN VII
Parotid glandCN IX
Ipsilateral Facial ParalysisBell's Palsy - Facial nerve/nucleus lesion
Upper and lower Facial ParalysisBell's Palsy - Facial nerve/nucleus lesion
Contralateral Facial ParalysisFacial motor cortex lesion (stroke)
Lower face paralysis Facial motor cortex lesion (stroke)
Jugular foramenCN IX
Lesion to CN X or nucleus ambiguus - uvula deviates to......away from side of lesion


Question Answer
Motor innervation of tongueCN XII (Hypoglossal)
Taste to anterior 2/3 tongueCN VII (Facial)
Sensation in anterior 2/3 tongueV3 (Trigeminal, Mandibular)
Taste to posterior 1/3 tongueCN IX: Glossopharyngeal
Sensation in poster 1/3 tongueCN IX ( Glossopharyngeal)
Taste in extreme posterior of tongueCN X (Vagus)
Taste in extreme posterior tongue: nucleusNucleus solitarius (NOT nucleus ambiguus)
Anterior 2/3Sensation: V3 (Trigeminal, Mandibular)
Taste: VII (Facial)
Motor: XII (Hypoglossal)
Posterior 1/3Taste and Sensation: CN IX (Glossopharyngeal)
Motor: CN XII (Hypoglossal)
Lesion to hypoglossal nerve or nucleus - tongue deviatestoward side of lesion

Hearing loss & facial lesions

Question Answer
conductive hearing loss rinneabnormal (bone > air)
conductive hearing loss weberpt hears the sound louder in the affected ear
sensorineural rinnenormal (air > bone)
sensorineural weberlouder in unaffected ear
noise-induced hearing loss damagestereocilliated cells in organ of Corti; high-frequency lost first
UMN lesionLesion between motor cortex and facial nucleus
Contra paralysis of lower face
forehead spared d/t bilateral innervation by UMNs
LMN lesionIpsi paralysis of upper & lower face
Bells PalsyLMN lesion.
Weber test256 Hz tuning fork is placed on the forehead
Rinne test512Hz tuning fork placed on mastoid bone. Once the vibration is no longer heard, quickly move tuning fork to just outside the ear canal. If they can hear it again, normal (air conduction should be better than bone)

Mastication muscles

Question Answer
muscles that close jawmasseter, temporalis, medial pterygoid
muscle that opens jawlateal pterygoid
all mastication muscles innervated byV3

Cranial nerve reflexes

Question Answer
afferent limb corneal reflexV1
efferent limb of corneal reflexVII
afferent limb of lacrimationV1
eff branch of lacrimationV11
aff limb of jaw jerkV3
efferent limb of jaw jerkV3
afferent limb of pupillaryII
efferent limb of pupillaryIII
afferent limb of gagIX
efferent limb of gagX
CN V motor lesionjaw deviates toward side of lesion
CNX lesionuvula deviates away from side of lesion
CNXI lesionweakness tunring head to contralalteral side of lesion (SCM). Shoulder droop side of lesion (trapezius).
CNXII lesion (LMN)tongue deviates toward side of lesion. atrophy fasiculations. No fasiculations then UMN and tongue away from esion.

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