lesions lecture

Question 1

Myasthenia Gravis

Answer 1

site of fault is at NMG; symptoms include weakness with sustained activity, drooping eyelids (ptosis), problems with speech

Question 2

level T10 Brown-Sequard

Answer 2

• corticospinal tract: ipsilateral paralysis below lesion
• dorsal column: sensory –> loss of position, vibration and touch ipsilateral below lesion
• spinothalamic tract: loss of pain and temperature opposite side starting two dermatomes below level of injury; loss of pain and temperature ipsilateral at zone of injury

Question 3

syringomelia

Answer 3

progressive cavitation around or near the central canal of the SC, usually in the cervical region
Progression of sxs as cavitation extends outward:
-lateral spinothalmaic fibers in ventral white commissure–> bilateral loss of pain and temp UEs both sides
-spinothalamic tracts not affected–> no LE loss of pain and temp
-Dorsal columns not affected–> position, vibration, light touch okay
-eventually reached anterior horn–> paralysis of muscles innervated by segments involved
-if reaches lateral corticospinal tract–> see UMN signs in LEs

Question 4

Tumor of CNVIII

Answer 4

loss of hearing, ipsilateral facial paralysis, ipsilateral reduced facial sensation, gait unsteadiness

Question 5

Hemiballismus

Answer 5

• uncontrolled rapid movements of proximal limb muscles
• unilateral stroke of subthalamic nucleus (of basal ganglia)
• treat with dopamine antagonists –> reduces impact of endogenous dopamine to reduce unwanted movement

Question 6

cerebellar damage sides

Answer 6

L cerebellum damage = L sided sxs

Question 7

damage to Broca’s area

Answer 7

Occlusion of middle cerebral artery supplying L frontal lobe Broca’s area
-Expressive aphasia = Broca’s aphasia –> can comprehend but can’t articulate

Question 8

damage to Wernicke’s area

Answer 8

Occlusion of middle cerebral artery supplying L temporal lobe Wernicke’s area
-Receptive aphasia = Wernicke’s aphasia –> can speak fluently but is nonsense (“word salad”) but can’t comprehend

Question 9

Global aphasia

Answer 9

both expressive and receptive aphasia, occurs with extensive damage to middle cerebral artery

Question 10

lesion to internal capsule

Answer 10

supplied by middle cerebral artery

-pure motor symptoms in face, UE, and LE

Question 11

lesion to posterior cerebral artery supplying thalamus and nothing else

Answer 11

pain and sensory loss

Question 12

decorticate rigidity/posture

Answer 12

coma patient presents with flexed UEs, clenched fists, and extended LEs
-damage restricted to cerebral cortex/corticospinal tract

Question 13

decerebrate rigidity/posture

Answer 13

coma patient presents with extended UEs, LEs, head, neck and back
-damage to brainstem below colliculi but above vestibular nuclei

Question 14

optic nerve lesion

Answer 14

total loss of vision in ipsilateral eye

Question 15

optic chiasm lesion

Answer 15

loss of vision in temporal halves of both field (bilateral heianopsia) b/c axons associated with receptors from nasal part of retina (temporal part of visual field) cross here
-only lesion in visual system causing a nonhomonymous deficit, i.e., deficit in two different part of visual field resulting from a single lesion

Question 16

optic tract lesion

Answer 16

loss of vision in opposite half of visual field (contralateral homonymous hemianopsia)

Question 17

optic radiations lesion

Answer 17

loss of vision in upper quadrant of opposite 1/2 of visual field (upper contralateral quadrantic hemianopsia)
-after leaving lateral geniculate, the optic radiation contains fibers representing both retinas

Question 18

lesion to upper and lower banks of calcarine sulcus of striate cortex

Answer 18

parietal loss in contralateral hemifield
-all cortical lesions show sparing of central visual field b/c foveal representation is extensive and single lesion unlikely to destroy entire representation

Question 19

MRI

Answer 19

• based on magnetic properties of tissue nuclei
• spinning nuclei alight with magnetic field and emit a weak electrical signal
• image depends on amount of water is tissue and timing of pulses

Question 20

advantages of MRI

Answer 20

• greater detail than CT
• any plane so 3D reconstruction
• picks up subtle changes not visible on CT
• Can enhance with gadolinium, reveals disruption of blood-brain barrier

Question 21

disadvantages of MRI

Answer 21

• claustrophobia
• can’t image people on life support or who have pacemakers
• cannot image people with ferrous implants or debris in eye
• can’t use on pregnant women (effects of magnetisum on fetus unknown)

Question 22

CT

Answer 22

x-ray emits series of beams in complete 360 degree arc around head, x-ray energy recorded, reconstruct so each pixel represents volume (voxel) of tissue, “slices of brain”

Question 23

advantages of CT

Answer 23

rapid, inexpensive, easy to monitor patient during process

Question 24

disadvantages of CT

Answer 24

brainstem view limited by nearby dense bone, images in one plane only, not 3D