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Neuro USMLE
Question | Answer |
---|---|
CN I innervates? Syndrome to look for and its cause? | smell; Kallman's syndrome=anosmia and hypogonadism due to gonadotropin rel hormone defic |
CN8 innerv? Defic causes? | (vestibulocochlear nerve) for hearing and balance; defic: deafness, tinnitus, vertigo |
CN9 innerv? Defic causes? | (glossopharyngeal) pharyngeal mscles, afferent gag reflex, parotid, taste in P 1/3 tongue, skin external ear; defic: loss of gag and loss of taste P 1/3 tongue |
CN10 innerv? Defic? | (vagus) palate, pharynx, larynx, abd viscera, skin of ext ear; defic: hoarseness, dysphagia, loss of gag or cough |
CN 11 innerv? Defic? | (spinal access nerve) sternocleidomastoid, trapezius; defic: can't turn head to side opp to lesion, shoulder droop |
CN 12 innerv? Defic? | (hypoglossal) innervates tongue; defic: tongue on protrusion deviates ipsi |
name 3 spinal tracts and their fxns | corticospinal=mvmt contra limbs, dorsal column=tactile, vibration, sensation; spinothalamic=pain, temp |
CNV innervates | (aka trigeminal nerve) mastication and facial sensation, afferent limb corneal reflex |
characteristics trigeminal neuralgia, treatment, rule out other diagnoses | (CN V) unilateral shooting pains in face, incl w brushing teeth, tx: carbamazepine [could be MS, or if bilateral could be stroke] |
CN3 fxn | eye mvmt, pupil constriction, accomodation, eyelid open |
CN4 fxn | eye mvmt |
pneumonic for which CN are sensory, motor | Some say marry money but my brother says big brains matter most |
pneumonic for eye mvmt mscls innerv | LR6SO4R3-lateral rectus=VI, superior oblique=IV, rest=III |
how differentiate CNIII, IV, V, VI, and VII problems wrt to eye exam | III: eye is down and out and can only move laterally, IV: can't look down when medial, V/VII: blink reflex, VI: can't look lateral |
nerves involved in pupillary reflex; 2 types of reflexes | CN II to sense light, III to constrict pupil; direct reflex if light was in that eye, consensual reflex if light was in other eye |
nerves involved in blink reflex | ophthalmic branch (V1) of CN V to feel stimulus, CNVII to close eyelid |
if L optic n damaged, what see on pupillary reflex | stimulating L eye causes no response in either eye, stimulating R causes both to respond |
if L occulomotor n damaged, what see on pupillary reflex | stimulating L eye causes R to respond, stimulating R eye causes R to respond |
characteristics CN7 UMN? LMN? MC cause for each? | UMN=contralateral lower facial paralysis **forehead is spared, usu cause is stroke; LMN=ipsi upper and lower facial paralysis, **forehead is involved on affected side, usu due to Bell's palsy or tumor |
Bell's palsy-- how can be difft from CNVII LMN? Causes? | can also have hyperacusis (noises loud) bc stapedius muscle is paralyzed; MC causes: AIDs, Lyme, sarcoid, tumor, DM |
how difft UMN from LMN | UMN have incrsd tone, spastic, and DTR (although initially may be decrsd for ea) + Babinski's; LMN has decrsd tone, flaccid and DTR, atrophy, fasciculations |
nerve for ea DTR | achilles=S1,2; knee=L3,4; biceps=C5,6; triceps=C7,8 [just count up] |
what number cause of death is stroke? % isch v hemorrh | number3, 85% isch |
how define TIA; usu cause/type | neuro deficit for <24hrs, (usu <30min). Usu embolic and high risk of stroke in next mos. |
characteristics of carotid stroke/TIA | loss speech, paralysis/paresthesia/clumsy contra extremity; can have amaurosis fugax (chol emboli to retinal/ophthalmic artery causes ipsi vision loss) |
define amaurosis fugax | chol emboli to retinal/ophthalmic artery causes ipsi vision loss |
characteristics of vertebrobasilar stroke/TIA | dizziness, dbl vision, vertigo, numb ipsi face & contra limb, dysarthria, hoarseness, dysphagia, HA, projectile vomitting, drop attacks |
what paradoxial stroke | venous clot goes through ASD/VSD/PFO and into head |
4 causes/types stroke/TIA | embolic (MC, usu from heart), thrombotic (usu atheroscl), lacunar (small vessels), non vascular (anoxic injury, low CO) |
describe subclavian steal and sympt | stenosis of subclavian before vertebral, so retrograde down vertebral artery to back fill subclavian; BP less in that arm and claudication when exercise that arm |
causes of stroke in younger pts | OCP, preg, hypercoag (prot C, S), cocaine, amphet, polycythemia, SC |
risk factors for stroke, which most impt | Age, HTN most impt; smoking, DM, hyperlipid, A Fib, CAD, prev stroke, Fm Hx, carotid bruits |
MC embolic stroke site | MCA |
sympt MCA stroke | aphasia (if L (dominant)), neglect/apraxia/confusion (if R), contra paresis face and arm, gaze twd lesion, homo hemianopia |
stroke a cerebral artery causes | contra paresis and sensory loss in leg (incl foot drop, gait dysfunction), amnesia, personality changes, cognitive changes [this artery also supplies frontal lobes] |
stroke posterior cerebral artery causes | homo hemianopia, memory deficits, dyslexia/alexia |
stroke basilar artery | coma, locked in syndrome, CN palsies, apnea, visual symptoms, dysphagia, dysarthia, drop attacks, **crossed weakness/sensory affecting ipsi face and contra body |
MC site circle of willis aneur | anterior communicating |
anterior communicating artery aneur sympt | bitemp hemianopsia + frontal lobe |
posterior communicating artery aneur sympt | CNIII (often see first impaired pupillary light reflex, unlike isch CNIII where that is spared until late] |
cerebral v subcortical strokes | cerebral: contra motor or sensory face, arms, trunk not usu legs (interhemisph), aphasia if L, visual/spatial more if R; subcortical: hemiparesis is complete (tracks all run together thru internal capsule) |
key plegias from brainstem | crossed, ipsi face, contra body |
how to differentiate peripheral neuropathy from myopathy | peripheral neuro: usu asymm, weakness more distal, can have sensory; myopathy: symm w weakness prox>distal, nml sensation |
how difft NMJ v peripheral neuro or myopathy | NMJ: fatigability, nml sensation |
general features of spinal cord injury, that are unique to these lesions | decrsd sensation below a sharp band |
general features of radiculopathy | pain! Affects muscles supplied by that root (myotome), and sensory area supplied by that root (dermatome) Weakness, atrophy, sensory deficit in a dermatomal pattern |
general features Cb lesion | incoord, intention tremor, ataxia |
general features of brainstem lesion | cranial nerve and spinal cord findings; ipsi face and contra body hemiplegia |
fxn radial nerve lesion | no supination, no extension (radial is SUPER), w wrist drop, sensation back hand finger 1-3 |
fxn ulnar nerve lesion | can't cross fingers or V sign, sensation 1/2 of ring finger and pinkie |
fxn median nerve lesion | can't flex fingers of wrist, thenar eminence atrophied (ie carpal tunnel), sensation 2,3,1/2 of ring from underside to nails, loss pronation. Thumb's up, all's ok when you flex yr nail polish w carpal tunnel |
axillary n lesion | innerv deltoid, can't abduct to horiz |
long thoracic n injury (metastetcomy) | serratus anterior, winged scapula, can't abduct past horiz |
common peroneal n lesion | foot drop, anterolateral sensation leg |
femoral n lesion | paralysis of quad, can't extend leg and loss of knee jerk, sensation anterior thigh |
upper brachial plexus lesion | Erbs palsy, arm by side, rotated inward, waiter's tip. Can't abduct arm, felx elbow or supinate |
lower brachial plexus lesion | Klumpke, median/ulnar n; clawed hand and Horners |
fxn of interosseus | palmar adduct, dorsal abduct PAD DAB |
how long might it take for isch stroke to show by non contrast CT | 24-48hrs |
what order if present s/s acute stroke | non contrast CT, ECG, CXR, CBC, PT/PTT, Lytes, Glu, caortid U/S, Echo |
when to tx acute stroke w tPA | <3hrs no contraindications, incl: prior hemorrh stroke, sz w onset stroke, stroke or head trauma w/in 3mos, HTN BP>185/110, BG<50 or >400, age <18, bleeding (GI, urinary <21d), plt <100K, INR>1.7 or elev PTT, surg<14d, recent MI, think TIA (rapid improve) |
tx of acute stroke other than maybe tPA | 1) ASA (don't give if tPA), 2) tx HTN only if >220/110, 3) treat F, hyperglu |
once give tPA what must control | BP <185/110 |
longterm tx s/p stroke | ASA if sm vessel dz, manage risk factors (HTN most impt, also DM, hyperlipid, etc), carotid endartectomy if nec |
epidural bleed: describe clinical present and anatomy (where blood is, how appears on imaging) | lucid interval, often temporal bone fx m. meningeal artery; biconvex blood bw dura and skull |
subarachnoid hemorr: describe clinical present and anatomy (where blood is, how appears on imaging) | worst headache, ruptured berry aneurysm (MC A. commun artery, blood in CSF, blood bw pia and arachnoid) |
subdural bleed: describe clinical present and anatomy (where blood is, how appears on imaging) | elderly pts, EtOH, may not remember fall, bridging veins, blood bw dura and arachnoid, crescent moon shaped on imaging |
order of compartments for cranial bleeds moving from brain surface outwards | pia-[subarachnoid space]-arachnoid-[subdural space]-dura-[epidural space]-skull |
clinical signs transtentorial (central) herniation | bilateral small and reactive pupils, Cheyne-Stokes respirations, flexor or extensor posturing |
clinical signs uncal herniation | CNIII gets entrapped, fixed and dilated ipsilateral pupil [from mass in middle fossa] |
clinical signs cerebellar tonsillar herniation | compression medulla, respiratory arrest, usu rapidly fatal [from mass in posterior fossa] |
describe Cushing triad | from incrsd ICP: HTN, bradycardia, repir irreg |
cerebral perfusion is determined by | MAP-ICP (nml ICP 5-15) |
MC location intracranial hemorrh | BG (66%), then Pons and Cb ea 10% |
key clinical factors suggesting intracranial hemorrh | focal neuro deficit that WORSENS over next 30-90min, AMS, signs incrsd ICP |
how pupils help differentiate place of intracranial hemorrh | pin point=pons, poorly reactive=thal, dilated=putamen |
tx intracranial hemorrh (after CT confirms) | control BP if >16-180/105, but slowly, if elevated ICP give mannitol and diuretics…surgery maybe for Cb hematomas, otherwise no |
if CT in suspected SAH is negative, what do | LP, diagnostic if xanthochromic (yellow CSF) bc means RBC have been there for a while (v traumatic tap) |
once SAH diagnosed, what do | cerebral angiography and call neurosurg; quiet rest in dark room w head elevated and stool softeners, nifedipine for vasospasm, control HTN |
name 5 key adult brain tumors | glioblastoma (type IV astrocytoma), meningioma, schwannoma, oligodendroglioma, pit adenoma |
name 5 key pediatric brain tumors | pilocytic atrocytoma, medulloblastoma, ependymoma, hemangioblastoma, craniophrangioma |
name where ea of 5 pediatric tumors occur: pilocytic atrocytoma, medulloblastoma, ependymoma, hemangioblastoma, craniophrangioma | pilocytic atrocytoma=P fossa, medulloblastoma=Cb, ependymoma=4th ventricle, hemangioblastoma=Cb, craniophrangioma=supratentorial |
what are the 3 MC primary adult brain tumors, in order | 1) glioblastoma, 2) meningioma, 3) schwannoma |
which primary brain tumor is found in the cerebral hemispheres and can cross the corpus callosum | glioblastoma |
majority of adult primary brain tumors are supra or infratentorial? Pediatric? | adult are usu supratentorial, pediatric are infratentorial |
what brain tumors suspect for hydrocephalus in kids | ependymoma (4th ventricle), medulloblastoma (Cb but can compress 4th v) |
what brain tumor assoc w von Hippel Lindau | hemangioblastoma in Cb |
what brain tumor can cause bitemporal hemianopia (so confused w pituitary adenoma) | craniopharyngioma (benign childhood tumor, MC childhood supratentorial tumor) |
supratentorial tumor in kid--think what? Benign or malignant? | craniopharyngioma, benign |
diffusely infiltrating brain tumor in P fossa in child, dx? Benign or malignant? | pilocytic astrocytoma, benign |
MC primary CNS neoplasm, characteristics | astrocytoma (ie glioblastoma), arise IN cerebral hemispheres, infiltrate brain w indistinct boundaries and can cross corpus callosum |
besides astrocytomas, what cancers appear in parenchyma? | mets (50%)-in order of freq: Lung, breast, melanoma, kidney, GI |
differential for ring enhancing lesion | met, brain abscess, glioblastoma multiform, lymphoma, toxo |
name 2 extraparenchymal brain tumors | meningioma, scwhannoma |
are schwannomas unliateral or bilateral? Assoc? | always unilateral, if bilateral then its NF II |
describe population that get meningiomas | usu 40-50, females >2x than males |
how do meningiomas appear on imaging | extracerebral, rounded w well-defined dural bases that compress underlying brain |
schwannomas--malignant or benign? | benign (no malignant potl) |
where schwannoma arise? Presenting symptom? | cerebellopontine angle, involved 8th cranial; first present w hearing loss (+/- tinnitus, loss of balance, nystagmus) |
schwannoma and meningioma--surg excision? | yes, although meningiomas have high recurrence rate |
calcified lesion external to brain parenchyma in adult--think what? | meningioma |
4 types of MS | 1)clinically silent/stable/benign (may progress late), 2) relapsing and remitting (MC), 3) 2ry progressing (relaps/remit gradually worsens), 4) 1ry progressive |
key clinical features MS | white matter plaques; scanning speech, intention tremor/INO/incontinence, nystagmus. Also optic neuritis w sudden vision loss |
describe INO, where injury is | injury medial longitudinal fasculus (MLF), If R MLF is affected and pt looks L, the R eye can't adduct and stays midline while the L abducts and start nystagmus (pt also sees dbl looking L) |
tx acute MS attack | hi dose IV steroids can shorten but won't alter overall progression dz, most attacks resolve <6wks |
disease modifying MS tx | INF, can cause flu-like sympt. Only use cyclophosphamide and other non specific immunomodulators in rapidly progressive bc many SE |
Rx for mscl spasticity in MS | baclofen (deriv of GABA) |
neurpathic pain tx | carbamazepine (Na channel) or gabapentin (neurontin, GABA analog) |
describe Guillan Barre clinical progression | infxn (often URI) or immun 1 wk before, symmetric distal weakness starts in legs w loss DTR **sensation intact, ascending paralysis, watch for respir paralysis (use spirometry to monitor) |
treatment Guillan Barre | usu stops spontaneously, plasmaphoresis reduces severity and length **don't give steroids, could make it worse! |
mech MG | autoantibodies Ach R at NMJ |
key characteristics MG clinically | mscl fatigue, esp extraocular, often asymm prox mscl wknss at end of day |
compare Lambert-Eatn Myasthenic syn to MG | Lambert-Eaton is often w SCLC, Ab to Ca++, sympt get better with use |
test for MG | 1) auto Ab (20% neg), 2) edrophonium (Tensilon, anticholinesterase) improves sympt |
what extra diagnostic need MG | CT to evaluate thymoma (10-15% on scan), but histol abnl ~75% |
tx MG longterm | pyridostigmine, steroids if not responding |
vit B12 and Friedrich ataxia damages which neural tracts, signs on exam? | demyelin of dorsal columns, corticospinal, and spinoCb; ataxic gait, hyperreflexia, impaired position/vibration sense |
describe Friedrich's ataxia (genes, pathophys, clinical) | AR triple repeat expansion dz of mitochondria; leads to demyelin of dorsal columns, corticospinal, and spinoCb; ataxic gait, hyperreflexia, impaired position/vibration sense |
describe syringomyelia (pathophys and clinical) | (basically a cyst of CSF) crossing fibers of [spinothal tract I think] are damaged; leads to bilateral loss of pain and temp sensation in shoulders (capelike distrib), +/- muscle atrophy hands |
what leads to destruction of anterior horns spinal column? Cause? Symptoms? | polio and werdnig-Hoffman; flaccid paralysis (LMN) |
occlusion ventral spinal artiery causes what? Clinical? | damages everything except dorsal columns, so only have tactile, vibration, sensation |
3 syphillis, aka? Damages? | tabes dorsalis damages dorsal roots and columns; impaired propioception and locomotor ataxia |
symptoms of ALS (amyotrophic lateral sclerosis=Lou Gehrigs)? | asymmetric, progressive weakness, UMN and LMN signs (spasticity, hyperreflex, + Babinski AND fascicul, atrophy, flaccidity); treatment is supportive |
pyramidal tract aka | corticospinal=mvmt contra limbs |
Pseudotumor cerebri-describe what it is and how it presents | incrsd ICP papilledema, daily headaches worse in am +/- N/V; young obese women |
Pseudotumor cerebri-describe how diagnose and treat | CT, MRI negative; concern about vision loss; treatment supportive w wgt loss and lumbar puncture or CSF shunt |
Pseudotumor cerebri-potl causes | large doses vit A, tetracyclines, wdrawal from corticosteroids can cause |
differentiate resting tremor, intention tremor, and hemiballsimus as to causes | hemiballismus (involuntary, unilateral flailing limbs) from subthalamic nucleus, intention tremor due to Cerebellar dz, resting tremor due to basal ganglia |
Brown-Sequard syndrome--distrib of lesion and clinical findings | hemisection of spinal cord; contra pain and temp, ipsi hemiparesis and ipsi loss of position/vibration (dorsal columns) |
what Rx may help extend life ALS | rituzole (glutamine blocking agent) |
2 main types of sz, which more common | partial (70%), generalized |
subtypes of partial sz | 1) partial; simple partial (consciousness intact), complex=LOC, postictal, may have automatisms, olfactory or gustatory halluc |
subtypes of generalized sz | tonic-clonic, absence (45% of these can have minor clonic, ie eye blinking) |
what's name of paralysis s/p seizure | Todd's paralysis, can last hrs-days |
tx generalized tonic clonic or partial sz | phenytoin and carbamzepine |
tx for absence sz | ethosuximide and valproate |
describe Rinne test | vibrating tuning fork on mastoid until they can’t hear it, then move to outside ear—they should be able to hear (+ test). |
describe Weber test | tuning fork on forehead, which side is louder |
outcomeof Weber/Rinne if conductive loss | abnl (-) Rinne (bone conduction>air); Weber louder in affected (think of cotton in yr ear) |
outcome Weber, Rinne if sensorineural loss | nml (+) Rinne (air >bone conduction); Weber louder in unaffected (good) side |
types of Vertigo (4) | 1) Peripheral: benign positional, Meniere's, labyrinthitis; 2) central (tumor, CVA, MS) |
how test for benign positional vertigo in the office | have pt go rapidly from sitting to laying while turning head->should reproduce |
describe Meniere's dz and px | thgt 2/2 fluid retention, recurrent severe vertigo, tinnitus, hearing loss lasting for hrs to days; recur mos-yrs later and hearing loss eventually permanent |
tx Meniere's | low Na diet, diuretics, maybe also anti chol and anti His [meclizine] |
when pt falls w vertigo, which side do they fall to | same side as lesion |
dominant lesion in R handed person? L handed? | 95% R handed are L dominant, 50% of L handed are L dominant |
describe location of lesion and clinical presentation of Wernicke's aphasia | Posterior superior temporal gyrus, wordy receptive/sensory/fluent aphasia, use wrong or nonsensical words; they don't comprehend written or spoken language; can't follow commands or repeat |
describe location of lesion and clinical presentation of Broca's aphasia | expressive/nonfluent broken, short sentences but meaningful. Comprehension intact. Impaired repetition. Posterior inferior frontal gyrus |
describe conduction aphasia | can't repeat bc no cxn bw Broca's and Wernicke's |
defect causing L homo hemianopia w macula sparing | R visual cortex |
defect causing L homo hemianopsia | R optic tract |
defect causing L upper quad anopsia | R optic radiations in R temporal lobe |
defect causing L lower quad anopsia | R optic radiations in R parietal lobe |
defect causing L homo hemianopsia w macular sparing | R occipital lobe, from P cerebral artery occlusion |
lesion causing bitemporal hemianopsia | optic chiasm (usu pit tumor) |
define difft types of glaucoma, general features | open angle (90%): painless, incrsd intraocular P 20-30mmHg, progressive visual field loss, incsrd cup-to-disk on fundo exam; closed-angle: sudden ocular pain, see halos around light, intraocular P >30, N/V, sudden decrsd vision, fixed, mid-dilated pupil |
tx closed angle glaucoma | pilocarpine, oral glycerin and/or acetazolamide |
tx open angle glaucoma | can include b-blockers, a agonist, prostaglandins (latanoprost), acetazolamide |
types of macular degeneration | exudative wet=neovascular w sudden vision loss; atrophic/non exudative/ dry (90%)=yellow-white dposits drusen |
findings on fundo exam: cotton wool | HTN |
findings on fundo exam: dot blot hemorr | DM |
findings on fundo exam: neo vascul | DM |
findings on fundo exam: pale fundus, cherry spot | central retinal artery occlusion |
findings on fundo exam: tortorous retinal veins | retinal vein occlusion |
findings on fundo exam: focal yellow-white deposits | macula drusen (macula degeneration) |
findings on fundo exam: incrsd cup to disk ratio | glaucoma |
findings on fundo exam: blurred optic disk margins | papilledema or papillitis |
differentiate fundo changes see with DM, HTN | DM: dot-blot hemorrhages, neovasc retina; HTN: ateriolar narrowing and cotton-wool spots and may see papilledema in severe HTN/HTN emergency |
common causes blindness in US, infxs causes (3) | DM in younger adults, macular degen in >55; river blindness (onch volvulus, a helminth, give ivermectin), chl trachomatis, toxo carnis (if granuloma) |
what's river blindness? What's the treatment | river blindness (onch volvulus, a helminth, give ivermectin), |
how recognize central retinal artery occlusion? Tx? Assoc? | sudden, painless, unilateral loss of vision; most common due to emboli (carotid, heart), but also temporal arteritis; no tx exc temporal arteritis give corticosteroids |
3 causes of sudden, unilateral vision loss, painless | 1) central artery occlusion (pale fundus, cherry red spot), 2) central vein occlusion (distended retinal veins, retinal hemorrhages), 3) retinal detach (pt reports floaters, flashes of light, curtain coming down) |
describe Sturge Weber | neurocutaneous dz; SKIN: congenital port wine stain (hemangioma), NEURO: leptomeningeal angio, glaucoma, sz, hemiparesis, MR |
describe tuberous sclerosis | neurocutaneous dz; hamartomas in skin, CNS, organs; astrocytoma, MR, sz **facial lesions with ash leaf spots, shagreen patches (thickened skin) |
describe neurofibromatosis | neurocutaneous dz; café au lait, axillary freckling, Lisch nodule (iris), neurofibromas in skin, neural tumors (meningiomas, acoustic neuromas), optic path glioma, Pheorenovascular HTN, scoliosis, sz |
NF1 v NF2 | NF1:café au lait, Lisch nodule (iris), gliomas, meningiomas, pheo, scoliosis; NF2: bilateral acoustic neuroma, juvenile cataracts (Step 1 pdf) |
von Hippel Lindau | neurocutaneous dz; **renal cell carcinoma, hemangioblastoma cerebellum, retinal angiomas, cysts in kidney and liver, pheochromocytomas, polycythemia, |
name 4 neurocutaneous dzs | Sturge Weber, tuberous sclerosis, NF, von Hippel Lindau |
NF2? Chromosome? Gene? | bilateral acoustic scwhannoma, juvenile cataracts; chrom 22, gene NF2 |
Lisch nodules are charact of? | (found in iris) Neurofibromatosis |
NF1 aka? Chromosome? | von Recklinghausen's disease=NF type 1; chrom 17 |
café au lait spots with normal IQ? With MR? with anemia? | nml IQ:NF; MR: McCUne Albright or tuberous sclerosis; anemia: Fanconi's anemia |
which neurocut has hamartomas (incl skin)? skin hemangioma? Skin neurofibromas? | hamartomas: tuberous sclerosis; skin hemangiomas: Sturge Weber and von Hippel-Lindau; skin neurofibroma: NF |
which neurocut has MR? | tuberous sclerosis, Sturge Weber |
describe corticospinal tract path and where decussates | Start in motor cortex, cross over in medulla, become LMN in anterior horn of spinal cord at that level. |
describe dorsal/posterior column tract path and where decussates | Start in mscl spindles, golgi tendon organs, Pacini&Meissner’s disks, signal through dorsal root ganglion up fasciculus gracilus and cuneatus (upper body), cross in medulla |
describe spinothal tract path and where decussates | Afferent/ascending. Start free nerve endings, pain fibers, cross at level of spinal cord (anterior/ventral white commissure), then go the length of the spinal cord to thalamus. |