ABPN Neuromuscular Medicine flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Upper motor neuron signs

Spasticity, hyperreflexia, Babinski sign, and loss of superficial abdominal reflexes indicate central corticospinal tract dysfunction rather than peripheral nerve or muscle disease.

Lower motor neuron signs

Fasciculations, muscle atrophy, hypotonia, and hyporeflexia reflect anterior horn cell, nerve root, plexus, or peripheral nerve dysfunction.

Demyelinating nerve conduction

Marked slowing of conduction velocity, prolonged distal latency, conduction block, or temporal dispersion suggests acquired or hereditary demyelinating neuropathy.

Axonal nerve conduction

Reduced compound muscle action potential or sensory nerve action potential amplitude with relatively preserved conduction velocity indicates axonal loss.

Fibrillation potentials timing

Spontaneous needle EMG activity from denervated muscle fibers appears roughly two to three weeks after acute nerve injury.

Myopathic motor unit potentials

Short-duration, low-amplitude, polyphasic motor unit potentials with early recruitment suggest muscle fiber disease rather than nerve disease.

Neurogenic motor unit potentials

Long-duration, high-amplitude, polyphasic motor unit potentials with reduced recruitment reflect reinnervation after chronic nerve injury.

Repetitive nerve stimulation decrement

A greater than ten percent drop in compound muscle action potential amplitude at low stimulation rates supports a postsynaptic neuromuscular junction disorder such as myasthenia gravis.

Preganglionic sensory sparing

Sensory nerve action potentials remain normal in root lesions because the cell body in the dorsal root ganglion is proximal to the injury.

Anterior horn cell disease

Progressive lower motor neuron signs with possible upper motor neuron signs and no sensory loss suggest conditions such as amyotrophic lateral sclerosis.

Conduction block

A drop in compound muscle action potential amplitude across a nerve segment with preserved distal amplitude indicates focal demyelination, as in compression or multifocal motor neuropathy.

H-reflex

The H-reflex assesses proximal sensory and motor conduction through the S1 root and is useful for suspected radiculopathy or polyneuropathy.

F-wave

F-waves reflect proximal motor nerve conduction and are prolonged in demyelinating neuropathies or root lesions.

Myotonic discharges

Needle EMG shows waxing and waning frequency and amplitude, described as a dive bomber sound, in myotonic dystrophy and other myotonic disorders.

Single-fiber EMG jitter

Increased jitter and blocking on single-fiber EMG is the most sensitive test for neuromuscular junction transmission defects such as myasthenia gravis.

Myasthenia gravis presentation

Fatigable ptosis, diplopia, and bulbar or proximal weakness worsening with activity suggest autoimmune postsynaptic acetylcholine receptor deficiency.

Myasthenia gravis antibodies

Acetylcholine receptor antibodies are positive in most generalized cases; MuSK and LRP4 antibodies identify seronegative forms with distinct treatment responses.

Thymoma screening

Chest imaging is indicated in myasthenia gravis because thymoma occurs in about ten to fifteen percent of patients and requires surgical evaluation.

Guillain-Barre syndrome

Ascending symmetric weakness with areflexia, albuminocytologic dissociation after the first week, and nadir within four weeks characterize this acute polyradiculoneuropathy.

Guillain-Barre treatment

Intravenous immunoglobulin or plasma exchange accelerates recovery; corticosteroids are not effective, and respiratory capacity requires close monitoring.

CIDP

Progressive or relapsing demyelinating polyneuropathy lasting more than eight weeks, treated first-line with IVIG, corticosteroids, or plasma exchange.

Amyotrophic lateral sclerosis

Progressive upper and lower motor neuron degeneration without sensory loss; riluzole and edaravone modestly slow disease progression.

Duchenne muscular dystrophy

X-linked dystrophin deficiency causes proximal weakness, calf pseudohypertrophy, elevated creatine kinase, and cardiomyopathy; corticosteroids slow functional decline.

Lambert-Eaton syndrome

Presynaptic voltage-gated calcium channel antibodies cause proximal weakness, hyporeflexia, and autonomic symptoms; small cell lung cancer must be excluded.

Dermatomyositis

Proximal weakness with elevated creatine kinase plus Gottron papules and heliotrope rash indicates an inflammatory myopathy with skin involvement.

Inclusion body myositis

Distal finger flexor and quadriceps weakness in an older adult with mildly elevated creatine kinase suggests this myopathy, which responds poorly to immunosuppression.

Length-dependent polyneuropathy

Distal symmetric sensory loss and weakness beginning in the feet reflect metabolic, toxic, or nutritional causes such as diabetes, alcohol, or vitamin B12 deficiency.

Charcot-Marie-Tooth disease

Hereditary motor and sensory neuropathy causing pes cavus, distal atrophy, and slowly progressive weakness, often with a family history.

Myotonic dystrophy

Autosomal dominant CTG repeat expansion causes distal weakness, myotonia, cataracts, cardiac conduction disease, and multisystem involvement.

Pompe disease

Acid alpha-glucosidase deficiency causes a proximal myopathy with respiratory weakness; enzyme replacement therapy is available and early diagnosis matters.

Rhabdomyolysis

Marked creatine kinase elevation with myoglobinuria risks acute kidney injury and requires aggressive intravenous fluid resuscitation.

Status epilepticus alternative

Not applicable to neuromuscular medicine; this card is excluded and should not appear in a neuromuscular examination.