lesions lecture Flashcards
Myasthenia Gravis
site of fault is at NMG; symptoms include weakness with sustained activity, drooping eyelids (ptosis), problems with speech
level T10 Brown-Sequard
- 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
syringomelia
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
Tumor of CNVIII
loss of hearing, ipsilateral facial paralysis, ipsilateral reduced facial sensation, gait unsteadiness
Hemiballismus
- 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
cerebellar damage sides
L cerebellum damage = L sided sxs
damage to Broca’s area
Occlusion of middle cerebral artery supplying L frontal lobe Broca’s area
-Expressive aphasia = Broca’s aphasia –> can comprehend but can’t articulate
damage to Wernicke’s area
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
Global aphasia
both expressive and receptive aphasia, occurs with extensive damage to middle cerebral artery
lesion to internal capsule
supplied by middle cerebral artery
-pure motor symptoms in face, UE, and LE
lesion to posterior cerebral artery supplying thalamus and nothing else
pain and sensory loss
decorticate rigidity/posture
coma patient presents with flexed UEs, clenched fists, and extended LEs
-damage restricted to cerebral cortex/corticospinal tract
decerebrate rigidity/posture
coma patient presents with extended UEs, LEs, head, neck and back
-damage to brainstem below colliculi but above vestibular nuclei
optic nerve lesion
total loss of vision in ipsilateral eye
optic chiasm lesion
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
optic tract lesion
loss of vision in opposite half of visual field (contralateral homonymous hemianopsia)
optic radiations lesion
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
lesion to upper and lower banks of calcarine sulcus of striate cortex
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
MRI
- 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
advantages of MRI
- 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
disadvantages of MRI
- 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)
CT
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”
advantages of CT
rapid, inexpensive, easy to monitor patient during process
disadvantages of CT
brainstem view limited by nearby dense bone, images in one plane only, not 3D
