Neuroanatomy/Spinal Cord Flashcards
66 yo p/w gait difficulty x2 yrs
- hypertonic legs, brisk reflexes, b/l upgoing toes, impaired joint position sense
- recently become paranoid
Dx
Dx = B12 deficiency: causes combined damage of corticospinal tract and dorsal columns in the spinal cord
Which CN are responsible for the corneal reflex
Afferent limb = CN V (trigeminal)
Efferent limb = CN VII (facial)
Define Chiari malformation
Congenital d/o of downward herniation of the cerebellar tonsils into the foramen magnum
- one of the leading causes of a syrinx
- often manifests w/ headaches and cerebellar symptoms
Which will cause a ‘pupil spearing third’ nerve palsy- microvascular disease (diabetes) or compressive lesion
Parasympathetic fibers run on the periphery of the EOM motor fibers => compression lesion will cause enlarged pupil
While pathology in the nerve itself will cause EOM weakness w/o pupillary dilation = ‘pupil sparing third’
Oxcarbazepine and OCPs- why shouldn’t you combine these?
Carbamazepine/tegretol (AED) increases metabolism of OCPs => makes OCPs less efficacious
So oxcarbazepine will decrease the efficacy of the OCPs
If pt loses temp/pain/fine touch/vibration on the same side of the body, localize the lesion
Above the inferior medulla (where the dorsal column tract decussates) b/c underneath that they are running contralaterally
What is pure word deafness?
(a) Locate the lesion
Pure word deafness = pts can hear, speak, and write, but cannot recognize spoken language
-often think ppl are speaking in another language
(a) Lesion of b/l primary auditory cortex
- needs to be b/l b/c hearing has b/l representation in the CNS => pts cannot become deaf from unilateral CNS lesion
Dorsal columns
(a) Fxn
(b) Location of synapses
(c) Location of decussation
(d) Final destination
Dorsal columns
(a) Vibration/fine touch, proprioception
(b) Synapses
- dorsal root nuclei of the lower medulla
- again at the VPL of the thalamus
(c) Decussates
- decussates in the lower medulla forming flattening called the medial lemniscus
(d) Primary somatosensory cortex (postcentral gyrus)
Pt presents w/ diplopia after being hit in the eye w/ a softball a few months ago
-notice head is tilted towards the right shoulder at rest
Localize the lesion
Lesion localizes to the left trochlea nerve (CN IV)
CN IV controls the superior oblique (SO4) that depresses and intorts the eye => get vertical diplopia when it’s out, so pt compensates by tilting head towards the unaffected side
-can’t downward intort the left eye, so tilt right head down to equilibrate
-often injury is 2/2 trauma
Which sensory modalities go thru the thalamus?
All except olfaction
Olfaction (smell thru olfactory bulbs CNI) is the only sensory modality which bypasses the thalamus
Which (if any) of the CNs decussate?
(a) Resulting innervation
CN IV (trochlear) is the only one that decussates
(a) Right CNIV innervates the left superior oblique
- while left trochlear innervates the right superior oblique (SO4)
Manifestations of posterior cord syndrome
2/2 occlusion of the two posterior spinal arteries => knocking out both dorsal column pathways = loss of proprioception
-often pts experience intense pain and burning sensations in their limbs
56 yo F w/ h/o EtOH abuse p/w gait difficulties x2 yrs
- wide based gait, positive Romberg’s
- mildly ataxic on finger to nose, strength is intact
Likely MRI finding
Atrophy of the cerebellar vermis
Damage to left frontal lobe (left frontal eye fields) would cause gaze preference to which direction?
Frontal eye fields deviate the eyes to the opposite direction, so left frontal eye fields deviate eyes to the right
Damage to left frontal lobe = eyes can’t deviate to the right = gaze preference to the left
-so gaze preference is to the same side of the lesion
What is glossopharyngeal neuralgia?
Similar to trigeminal neuralgia (episodes of electrical shock sensation), pain in the posterior tongue and pharynx
Spinothalamic tract
(a) Fxn
(b) Location of synapses
(c) Location of decussation
(d) Final destination
Spinothalamic tract
(a) Pain/temp sensation
(b) Synapses twice
- dorsal root ganglion
- VPL of the thalamus
(c) Decussates once at the anterior commissure 1-2 levels above entering the spinal cord
(d) Primary somatosensory cortex = Postcentral gyrus
What is the conus medullaris?
Termination of the spinal cord at L1/L2
Physical exam finding indicating APD (afferent pupillary defect)
APD: when you do swinging light test and you don’t get direct and consensual pupil response b/l
- APD = affected eye paradoxically dilates light swung from unaffected to affected eye
- -both pupils constrict when light held in front of unaffected eye
Indicates lesion of the optic nerve
Tx for Bell’s palsy
Oral steroids and acyclovir
-acyclovir beneficial if started early in the course of the illness
Just in case the Bell’s palsy is 2/2 herpes zoster infxn of CN VII: presents w/ painful rash in the ear canal and dysfunction of CN VII (and sometimes VIII)
Where does the sympathetic nervous system originate?
Nucleus in the intermodeiolateral cell column of vertebral levels T1-L2
Hallmark eye finding of PSP
(a) Localize lesion
Restricted upgaze = upgaze palsy
(a) Lesion localizes to pineal gland
- pinealoma similarly presents w/ upgaze palsy
Origin of motor fibers for CN IX and X
Nucleus ambiguus = group of motor neurons in the medulla
Origin of the parasymp fibers of the oculomotor nerve
Parasympathetic fibers of CN III originate in the Edinger-Westphal nucleus of the brainstem
Tremor seen in cerebellar injury
Intention tremor
- increases during purposeful movement
- oscillation increases as the target is reach
Where would pain/temp sensation be lost due to lesion of the left spinothalamic tract at T10
Spinothalamic tract enters dorsal horn, then ascends 1-2 levels as it decussates across the anterior grey commissure
=> lesion at T10 causes loss of pain/temp on contralateral dermatome 1-2 below, so loss of pain/temp of the right T11/T12 dermatome
ALS
(a) What degenerates?
(b) Findings on EMG
(a) Degeneration of motor neurons of the brain, CN nuclei, and spinal cord (anterior horn cells)
- basically all motor neurons
(b) EMG findings:
fasciculations, fibrillations, sharp waves
24 yo F dx w/ optic neuritis
To help speed up recovery what do you give?
Solumedrol (IV steroids) then oral taper
Corticospinal tract
(a) Fxn
(b) Location of synapses
(c) Location of decussation
(d) Final destination
Corticospinal tract
(a) Motor signals: down from precentral gyrus or supplemental motor areas thru the internal capsule
(b) Synapses at the ventral/anterior horn of the level of exit in the spinal cord
(c) Decussates at the levels of the medullary pyramids in the lower medulla
(d) Nmj
Two etiologies to think of before diagnosing idiopathic Bell’s palsy
- If b/l- think Lyme disease
2. Sarcoidosis often presents w/ Bell’s palsy
Two etiologies of anterior cord syndrome
Anterior cord syndrome is due to occlusion of the anterior spinal artery
-seen in pts who become hypotensive, or have surgery on their abdominal aorta
Unilateral CN V injury
(a) Describe the impact on the muscles of mastication/
(b) Which brainstem reflex will be affected?
(a) Muscles of mastication have bilateral cortical innervation => unilateral CN V damage doesn’t cause weakness of jaw movements
(b) Corneal reflex (eye blinks if irritated), trigeminal nerve carries the afferent limb
- while facial nerve carries efferent limb
Describe manifestations of Bell’s palsy
- Weakness of facial muscles
- CN VII innervates orbicularis oculi, zygomaticus, levator labii superioris, depressor labii inferioris, buccinator, nasalis
Possible symptom of hyperacusis since CN VII innervates the stapedius muscle which dampers sound
- Dry eyes/dry mouth
- b/c CN VII innervates submandibular and sublingual glands - Decreased sensation of taste
- CN VII receives taste from the anterior 2/3 of the tongue
Clinical presentation of B12 deficiency
UMN signs and proprioceptive difficulties due to ‘combined damage’ of both the corticospinal tract and the dorsal column
Trigeminal nerve
(a) Sensory distribution
(b) Motor fxn
Trigeminal nerve = CN V
(a) Sensation of skin on the face
- V1,2,3
(b) Innervates the muscles of mastication
- only V3 has motor
Pt dragging right leg
-MRI shows intramedullary lesion on the right side of the spinal cord
Name another expected sensory finding
Decreased pain/temp sensation on the left
-spinal cord lesion: spinothalamic tract decussates at the anterior grey commissure 1-2 levels above entry in thru dorsal horn
Clinical presentation of optic neuritis
Blurry vision, pain w/ EOM
Specific sign: pt can p/w loss of color vision, especially the color red
Trigeminal neuralgia may be the presenting feature of what disease?
MS
Differentiate cauda equina and conus medullaris syndrome
Cauda equina
- gradual and unilateral
- bowel/bladder retention is a later finding
- decreased knee reflexes
- LE weakness often asymmetrical
Conus medullaris
- sudden and b/l
- bowel/bladder incontinence develop early
- knee reflexes are preserved
- weakness is symmetrical
Expected diagnosis in a pt w/ internuclear opthalmoplegia
Internuclear opthalmoplegia = lesion in the MLF (medial longitudinal fasciculus) connecting CNIII and CNVI
-problem w/ conjugate gaze: when right eye looks one way the left eye doesnt follow
Most commonly seen in MS
75 yo M p/w gait instability
- legs crossed in front of each other
- hyperreflexia, b/l Babinski
Dx
Dx = cervical spondylosis (spinal osteoarthritis)
-‘scissoring gait’ associated w/ UMN lesion: seen in spinal cord tumor, trauma, compression (cervical spondylosis)
Name some ototoxic drugs
- aspirin can cause tinnitus (ringing in ears)
- aminoglycoside abxs (-‘mycin’)
45 yo F wakes up w/ left facial droop
- trouble closing left eye, cannot wrinkle left face
- noises sound louder on the left, dull pain behind left ear
Dx?
Dx = Bell’s palsy = facial nerve palsy
-innervates muscles of facial expression = orbicularis oculi, smile muscle, also stapedius muscle (dampens sounds)
Which symptom bothers MS pts the most
Fatigue :-(
-lots of Adderall given to MS pts
Pt w/ NMO p/w intractable hiccups and nausea/vomiting
Locate the lesion
Lesion = area postrema
Left eye ptosis, dilated left pupil, eye deviated down and out
Localize the lesion
Lesion localizes to oculomotor nerve (CNIII)
CN III palsy
- ptosis due to loss of innervation to levator palpebrae superioris
- dilated pupil 2/2 loss of parasympathetics (which come from the Edinger-Westphal nucleus)
- down and out b/c loss of innervation to many EOM (all except superior oblique and lateral rectus)
What illegal substance interferes w/ B12 metabolism
Nitrous oxide (laughing gas)
What is the only FDA approved medication to slow the course of ALS
(a) Mechanism
Riluzole
(a) Extends survival by preventing stimulation of glutamate receptors
45 yo M w/ progressive weakness for months starting in right leg, progressing to left arm
- muscles have been ‘jumping’ recently
- weak in RLE and RUE
- muscle wasting of intrinsic hand muscles
- reflexes absent in right leg, brisk elsewhere w/ upgoing toe on left
Dx
ALS
-b/c both UMN and LMN findings
Define anisocoria
Anisocoria = difference in size of the pupils
Tell which pupil is pathologic by using light!
Constricted pupil in bright room is normal, while abnormal in dark room
In a pt w/ a unilateral spinal cord lesion, where would you expect the pain/temp abnormalities to begin on the body
Contralateral dermatomes 1-2 vertebrae below
-second-order neurons of the spinothalamic system ascend 1-2 levels as they cross in the anterior gray commissure
