Motor Neuron & Peripheral Nerve Disorders (Swenson) Flashcards
weakness with sensory changes and increased deep tendon reflexes suggests what 3 differential diagnoses?
stroke (cerebrum)
MS (brainstem)
tumor (spinal cord)
weakness with sensory changes and decreased DTR suggests what differential diagnosis?
peripheral neuropathy:
mononeuropathy (ie, carpal tunnel)
polyneuropathy (diabetics)
mononeuritis multiplex (vasculitis, polyarteritis)
weakness without sensory changes and increased DTR suggests what differential?
motor problem of the anterior horn cell (upper motor neurons), ie, ALS
Which of the following would NOT be on your differential for weakness without sensory changes and decreased DTRs?
A. Myasthenia gravis
B. Muscular dystrophy
C. Polymyositis
D. Poliomyelitis
E. Amyloidosis
E. Amyloidosis is a type of mononeuritis multiplex in which there is a build up of misfolded amyloid proteins that get deposited in organs, commonly the kidney and heart. This presents with weakness + sensory changes and decreased DTRs.
A 55 yo woman presents with numbness of her right thumb, right index finger, and right middle finger. The numbness is exacerbated by typing and holding the steering wheel while driving. She does get pain in her hand, which wakes her up at night. She has normal strength in arms and legs, normal reflexes. What is the localization of this problem?
A. Upper motor neuron in the anterior horn
B. Brain stem
C. Peripheral nerve
D. Neuromuscular junction
E. Spinal cord
C. Peripheral nerve.
Bonus: a lesion in what peripheral nerve is causing the patient’s symptoms?
answer: median nerve
A 34 yo woman presents with acute onset of progressive weakness in her arms and legs that started 4 days ago. She has loss of feeling in hands and feet and needs help standing and transferring; she is not able to walk. 2 weeks ago she had flu-like symptoms including diarrhea and nausea, which resolved within a few days.
PE: FVC 60% of normal. Facial weakness. Diffuse weakness in arms and legs with distal worse than proximal. Decreased vibratory sensation to knees and elbows. Absent reflexes throughout. Diagnosis?
Guillain-Barre syndrome
*most common form of acute inflammatory demyelinating polyradiculoneuropathy (AIDP), usually preceded by infection, ie CMV, EBV, campylobacter
GBS most commonly affects myelin, as opposed to axons
Why does Guillain-Barre Syndrome commonly follow an infection with organisms like campylobacter?
molecular mimicry to host peptides ► antibodies against Schwann cells and myelin ► segmental demyelination
A 57 yo woman presents to clinic with numbness and paresthesias in her feet up to the mid-shins. The symptoms started in her toes about five years ago and have slowly progressed. She has a history of type II diabetes with most recent HgA1c of 8%.
PE: normal strength aside from mild toe flexion weakness. Normal reflexes except Achilles tendon. Diminished vibratory sensation at the first MTP joint.
Diagnosis?
diabetic polyneuropathy
*thought to be due to hyperglycemia-induced metabolic sequelae (ie, hyperlipidemia, microvascular-hypoxic factors) and their effect on nerve axons.
shows stocking-glove pattern of sensory loss
polyneuropathy
Polyneuropathy most commonly affects axons as opposed to myelin
A 64 yo man presents with painless progressive weakness in right hand grip strength over the past six months. He has noticed muscle cramps throughout his legs and fasciculations (visible muscle twitching) in both triceps and in his tongue. He trips sometimes on toe walking and occasionally chokes when drinking water. He has no numbness or paresthesias and no bowel/bladder problems. PE shows some muscle atrophy in the intrinsic hand muscles of the right hand and brisk reflexes throughout. Diagnosis?
ALS
*patient is showing both upper motor neuron signs: hyper-reflexia, spasticity and lower motor neuron signs: muscle atrophy and fasciculations. No sensory changes - sensory nerves and DRG spared.
Bulbar-onset of ALS is associated with worse prognosis, affecting what 2 cranial nerves?
CN VII and X
Bonus: what are the 3 main presenting symptoms of bulbar-onset ALS?
Answer: dysarthria, dysphagia, dyspnea
Which of these is not a proposed mechanism for the pathogenesis of the disease that causes the gross findings below?
A. Glutamate excitotoxicity
B. Auto antibodies to myelin
C. Oxidative stress
D. Defects in protein folding
E. Mitchondrial dysfunction
F. Neuroinflammation
B. This was not a proposed mechanism of ALS mentioned in class.
Which of the following is NOT a clinical feature of a lower motor neuron lesion?
A. Muscle spasticity
B. Muscle cramps
C. Muscle atrophy
D. Muscle fasciculations
A. Muscle spasticity is an upper motor neuron symptom.
the most common etiology associated with this class of disorders is segmental demyelination at a site of compression
mononeuropathy
