Where's the lesion? Flashcards
What spinal tracts does polio damage? What kind of paralysis does this cause?
Anterior horns, causes LMN lesions leading to flaccid paralysis
What findings are seen in syringomyelia?
A cape-like, bilateral loss of pain and temp in upper extremities - results from a syrinx (CSF-filled cavity in the spinal cord) that expands and damages the anterior white commissure. Seen in 35% of Chiari malformations
What conditions can lead to facial nerve palsy?
AIDS, Lyme disease, Sarcoidosis, Tumors, and Diabetes
ALexander Bell with STD
What is a “blown pupil” suggestive of?
Impending ipsilateral brainstem compression
Where relatively in the brainstem is the dysfunction for decorticate vs decerebrate posturing?
Decorticate posturing indicates slightly more superior brainstem dysfunction (decerebrate slightly more inferior)
What are the likely causes of decreased consciousness in a patient with focal findings vs no focal findings?
Focal - structural causes (e.g. stroke, hemorrhage, tumor, abscess)
Focal signs absent - diffuse causes (e.g. metabolic, toxic, infectious, hypoxia)
Where’s the lesion that causes locked in syndrome?
Basilar artery infarction - leads to damage to the pons
What is damaged if there is a relative afferent pupillary defect?
Damage to the optic nerve of the eye that remains relatively dilated when light is shined in that eye. The affected eye will constrict consensually when light is shown into the “good” eye
How do hydroxyamphetamine eye drops help distinguish a preganglionic (1st and 2nd order) lesion from a postganglionic (3rd order) lesion in sympathetic fibers (Horner syndrome)?
The pupil will fail to dilate if it’s a 3rd order lesion but will dilate if it’s preganglionic
What does ptosis, dilated pupil (mydriasis) and ophthalmoplegia indicate (eye down and out)?
III nerve palsy
Note that CN III’s nucleus is in the midbrain
How do CN III nerve palsy’s present differently when compression vs diabetes is the cause?
The parasympathetic fibers run on the outside and motor fibers on the inside of the nerve so compression causes ptosis and mydriasis initially followed by motor problems (eye down and out). DM affects the blood vessels within the nerve primarily damaging motor functions
What does upbeating nystagmus indicate?
A lesion of the anterior cerebellar vermis and lower brainstem. Can also occur with drug intoxication and Wernicke’s encephalopathy
What does downbeating nystagmus indicate?
Disorders of craniocervical junction (Chiari malformation). spinocerebellar degeneration, MS, familial periodic ataxia, and drug intoxication
In vestibular nystagmus, what direction is the fast phase?
Away from the lesion
What lesion is responsible for conjugate gaze deviation?
The frontal eye field in the frontal lobe, eyes deviate towards the side with the lesion
What motor symptoms do lesions to the base of the pons cause?
Weakness of the ipsilateral face and contralateral arm and leg (“crossed signs”), because descending motor fibers to the face have already crossed at that level but not the body
What neurons are damaged in spastic vs atonic bladder?
UMN in spastic (e.g. frontal lobe, pons, suprasacral spinal cord) - causes urge incontinence; LMN in atonic bladder (e.g. conus mdullaris, cauda equina, sacral plexus, peripheral nerve) - causes overflow incontinence
Damage to where causes ballism or hemiballismus?
Contralateral lesion of the caudate, putamen, or subthalamic nucleus. Stroke is the most common cause, although hyperglycemia may also be a cause
What artery supplies the anterior horns, the STT, and the corticospinal tracts of the spinal cord?
The Anterior spinal artery (cephalad portion from the vertebral arteries and caudally from the aorta via the artery of Adamkiewicz). Anterior spinal artery syndrome is due to a stroke affected motor and pain and temp function below the lesion (posterior column function is usually spared)
What is Meralgia paresthetica?
Caused by entrapment of the lateral femoral cutaneous nerve near the inguinal ligament. Causes burning sensation and variable loss of sensation over the anterolateral thigh
What are features of peroneal neuropathy?
Due to entrapment of the peroneal nerve between the neck of the fibula and the insertion of the peroneus longus muscle. Presents with foot drop with minimal sensory complaints
A lesion of what part the brain can cause apraxia (inability to perform a learned motor task)?
The dominant frontal or parietal lobe
What does sudden onset of hypophonia (soft speech suggest)?
Subcortical (usually thalamic) lesion
Disease in what part the brain leads to intention/kinetic tremors?
Cerebellum
Damage to what nerve leads to clawhand/benediction sign (impaired extension of digits 4 and 5)?
Ulnar nerve (due to weakness in the lumbricals causing malpositioning of the extensor sheaths
What ocular nerve is most likely to be damaged with facial trauma?
CN IV because it extends farthest into the orbit
What area of the CNS is damaged with ocular bobbing (rapid downward deviation of eyes followed by slower conjugate gaze back up)?
Pontine damage
Damage to the STT causes loss of pain and temp sensation at what level relative to the lesion?
1-2 segments below the lesion because second order neurons ascend 1-2 levels before crossing the anterior white commissure
