Neuromuscular Disorders Flashcards
Most common category of polyneuropathy
Distal symmetric sensory
A nerve conduction study can differentiate radiculopathy from a plexopathy. How?
Sensory nerve action potentials are preserved in radiculopathy.
The most common cervical radiculopathy affects which nerve root
C7
Indications for surgical decompression in radiculopathy
- Moderate to severe weakness
- Worsening weakness / sensory loss
- Severe pain unresponsive to conservative measures
PE finding that raises suspicion for a brachial plexus lower trunk lesion
Atrophy of thenar eminence with sensory loss in medial hand / fingers
PERIPHERAL NERVE INJURIES
Localize the lesion.
- Scapular winging
- Weakness in external rotation of the shoulder
- Sensory disturbance in the lateral upper arm
- Long thoracic n
- Axillary n
- Axillary n
Match radial nerve lesion with presentation
- Sensory loss in posterior hand; elbow extension spared
- Wrist drop, finger drop, no sensory loss
- Weakness of all radial muscles, sensory loss in posterior arm/forearm/hand
A. Radial nerve at the axilla
B. Spiral groove of humerus
C. Posterior interosseous nerve entrapment
- B
- C
- A
Ulnar nerve lesion signs
- At rest, the fifth digit is slightly abducted due to weakness of third palmar intraosseous
- Curled thumb when trying to pinch (thumb adduction and index abduction weakness leads to weak pinch; to compensate, median-innervated FPL causes thumb flexion)
- Wartenberg’s sign
2. Froment’s sign
The only muscle below the knee with a contribution from the L4 root
Tibialis anterior
Most common lumbosacral radiculopathy affects which root
L5
Which nerve root is involved?
- Sensory deficit over posterolateral calf and foot (plantar aspect)
- Perineal and anal sphincter region
- Numbness over lateral leg and dorsomedial foot
- S1
- S2/S3/S4
- L5
Fat boy gained weight a bit too quickly and now started feeling numbness of the lateral thigh. Symptoms may be due to entrapment of which nerve.
Lateral femoral cutaneous nerve
Most common neurological cause of acute generalized weakness
Guillain-Barre Syndrome
In Guillan Barre syndrome, antibodies against these 4 organisms are seen.
- Campylobacter jejuni
- CMV
- EBV
- Mycoplasma
Ophthalmoplegia +
Gait ataxia +
Areflexia +
Mild limb weakness
Miller-Fisher variant of acute inflammatory demyelinating polyneuropathy
Associated with C. jejuni
IgG against GQ1b gangliosides
Classic sign of vasculitic neuropathies
Multiple mononeuropathies (mononeuritis multiplex)
Which of the following large vessel vasculitides can present with neuropathy:
Giant cell or Takayasu’s arteritis
Giant cell / temporal arteritis
What is the most common necrotizing vasculitis?
Polyarteritis nodosa
Acute onset of severe neuropathic pain in shoulder, sometimes arm and hand; lasting days to weeks replaced by weakness with little sensory disturbance
Brachial neuritis
aka neuralgic amyotrophy
aka Parsonage-Turner Syndrome
Progressive and widespread muscle stiffness.
Muscle twitching and cramps; persisting during sleep.
Associated hyperhidrosis, encephalopathy and insomnia.
Diagnosis?
What is the pathophysiology?
Isaac’s Syndrome
Antibodies against voltage-gated potassium channel; may be spontaneous or paraneoplastic
Most common cause of neuropathy in the world
Leprosy
Most commonly affected nerve roots in shingles
THORACIC > lumbosacral and cranial
Most common form of DM neuropathy
Distal symmetric sensory
Mees lines in the fingernails and toenails.
Acute abdominal pain, nausea, vomiting, diarrhea then distal paresthesias.
Axonal sensorimotor neuropathy.
Pancytopenia and basophilic stippling of RBCs.
Diagnosis?
Arsenic poisoning
Slow onset of upper -> lower limb weakness; classic is wrist and finger drop.
Motor axonal neuropathy; usually no sensory complaints.
Basophilic stippling of RBCs, microcytosis, and hypochromia.
Diagnosis?
Lead toxicity
Macrocytic anemia.
Decreased vibratory and position sense.
Weakness, hyperreflexia, Babinski sign.
Diagnosis?
B12 deficiency
Sensory ataxia, gait instability, Romberg sign, pseudoathetosis, sensory drift.
Non-length dependent sensory loss and hyporeflexia
Deficiency in which Vitamin?
Vitamin E
This drug is given to patients with amyotrophic lateral sclerosis to increase tracheostomy-free survival but without any effect on overall life expectancy
Riluzole
Distal -> proximal weakness. Temporal atrophy and jaw weakness. Delayed muscular relaxation after forceful contraction; improving with repetition.
Associated with mildly reduced intelligence, depression, cataracts, conduction abnormalities or cardiomyopathy, and diabetes.
Diagnosis?
Myotonic dystrophy type 1
Chanellopathies. Which channels are affected?
- Malignant hyperthermia
- Hypokalemic periodic paralysis
- Hyperkalemic periodic paralysis
- Ryanodine receptor
- Ca channel
- Na chanel
Triad of periodic paralysis, cardiac arrhythmias and skeletal abnormalities. What is the channel involved?
Andersen-Tawil Syndrome
Mutations in KCNJ2 (inwardly rectifying K channel)
