ABPMR Neuromuscular Medicine key terms

A progressive neurodegenerative disease in which upper and lower motor neurons degenerate, producing weakness, atrophy, fasciculations, spasticity, and often bulbar and respiratory involvement, with sensory function typically preserved.

Clinical and electrodiagnostic criteria for ALS that combine progressive upper motor neuron signs with evidence of lower motor neuron degeneration, counting fasciculation potentials as active denervation to improve diagnostic sensitivity.

An autosomal recessive motor neuron disease from loss of SMN1 function that produces symmetric proximal weakness and atrophy beginning in infancy or childhood, sparing sensation, cognition, and often facial muscles.

An X-linked CAG repeat expansion in the androgen receptor gene causing adult-onset bulbar and limb lower motor neuron weakness, gynecomastia, tremor, and sometimes mild large-fiber sensory nerve involvement.

New or worsening weakness, fatigue, and muscle pain appearing years to decades after acute poliomyelitis, attributed to degeneration of enlarged, reinnervated motor units rather than reactivation of virus.

A myelopathy of vitamin B12 deficiency damaging the dorsal columns and corticospinal tracts, causing paresthesias, loss of vibration and position sense, sensory ataxia, spastic weakness, and often macrocytic anemia.

Dysfunction of one or more spinal nerve roots, usually from disc herniation or spondylosis, producing dermatomal pain and weakness, atrophy, reflex loss, or sensory change in the corresponding segmental distribution.

The group of skeletal muscles innervated by the motor axons of a single spinal nerve root; clinicians use it to localize weakness, such as deltoid for C5 and quadriceps for L4.

Compression of lumbosacral nerve roots below the conus medullaris, causing saddle anesthesia, bladder and bowel dysfunction, asymmetric leg weakness, and areflexia; it requires urgent imaging and surgical evaluation.

An acute immune-mediated brachial plexus neuropathy with severe shoulder pain followed by patchy scapular or proximal arm weakness and atrophy, usually recovering incompletely over months to years.

Compression of the lower brachial plexus, usually at the scalene triangle, causing ulnar-predominant pain, paresthesias, and hand intrinsic weakness; nerve conduction studies are frequently normal.

A rapidly progressive immune-mediated demyelinating polyneuropathy causing ascending symmetric weakness, areflexia, and autonomic instability, with elevated cerebrospinal fluid protein and nadir generally within four weeks.

An immune-mediated demyelinating polyneuropathy with progressive or relapsing weakness lasting more than eight weeks, high cerebrospinal fluid protein, and multifocal demyelinating features on nerve conduction studies.

An immune-mediated motor neuropathy producing asymmetric distal arm weakness without sensory loss, persistent conduction block on nerve conduction studies, and frequent improvement with intravenous immunoglobulin.

The most common inherited demyelinating neuropathy, caused by a PMP22 duplication, producing slowly progressive distal leg and hand weakness, atrophy, pes cavus, and uniform marked nerve conduction slowing.

Necrotizing inflammation of epineurial blood vessels causing ischemic axonal nerve injury, typically presenting as painful, stepwise mononeuritis multiplex with asymmetric sensory and motor deficits.

Damage to thinly myelinated and unmyelinated nerve fibers producing burning distal pain, allodynia, and autonomic symptoms, with normal large-fiber conduction studies and reduced intraepidermal nerve fiber density.

Breakdown of the axon and its myelin distal to a nerve injury over days to weeks, producing denervation potentials on needle electromyography and loss of distal conduction responses.

A three-part grading of traumatic nerve injury: neurapraxia with conduction block and full recovery, axonotmesis with axonal loss but intact sheath, and neurotmesis with complete transection needing repair.

An autoimmune disorder in which antibodies against postsynaptic acetylcholine receptors or related proteins impair transmission, causing fluctuating, fatigable ptosis, diplopia, bulbar and limb weakness worsened by use.

Autoimmune myasthenia caused by antibodies to muscle-specific kinase, often with prominent bulbar, neck, and respiratory weakness, little ocular involvement, and limited benefit from pyridostigmine.

An autoimmune presynaptic disorder with antibodies to voltage-gated calcium channels causing proximal leg weakness, depressed reflexes, autonomic dryness, and often paraneoplastic small cell lung cancer.

Toxins from Clostridium botulinum block presynaptic acetylcholine release, producing descending symmetric weakness, bulbar palsy, mydriasis, and autonomic dysfunction after contaminated food, wounds, or infant exposure.

Inherited defects in presynaptic, synaptic, or postsynaptic proteins of neuromuscular transmission causing weakness from infancy or childhood, without autoantibodies, often responsive to specifically chosen medications.

Respiratory failure or severe bulbar dysfunction from worsening myasthenia, frequently triggered by infection, surgery, or medication change, requiring intensive care, airway assessment, and rapid immunotherapy.

An X-linked dystrophinopathy causing progressive proximal weakness, calf pseudohypertrophy, markedly elevated creatine kinase, and cardiomyopathy, with loss of independent ambulation in early adolescence.

An autosomal dominant CTG repeat expansion disorder causing distal weakness, myotonia, cataracts, cardiac conduction disease, and multisystem features, with genetic anticipation across successive generations.

An idiopathic inflammatory myopathy with proximal weakness and characteristic skin findings such as heliotrope rash and Gottron papules, driven by complement-mediated capillary injury and sometimes associated with malignancy.

An inflammatory myopathy of older adults causing slowly progressive, asymmetric weakness of finger flexors and quadriceps, with rimmed vacuoles on biopsy and poor response to immunosuppressive treatment.

A muscle channelopathy from calcium or sodium channel mutations causing episodic flaccid weakness with low serum potassium, often provoked by carbohydrate-rich meals, rest after exercise, or insulin.

A muscle disorder from mitochondrial DNA or nuclear gene defects causing exercise intolerance, weakness, lactic acidosis, and commonly multiorgan features such as hearing loss, diabetes, or seizures.

The summed response recorded over a muscle after supramaximal stimulation of its motor nerve; amplitude reflects the number of excitable motor axons and muscle fibers, and latency reflects conduction speed.

The response recorded over a sensory nerve or digit after stimulation, assessing large myelinated sensory axons and helping separate preganglionic root lesions from postganglionic plexus or nerve lesions.

The waveform recorded by a needle electrode from muscle fibers of a single motor unit firing near the tip; duration, amplitude, and morphology indicate neuropathic remodeling or myopathic change.

Spontaneous brief discharges of individual muscle fibers occurring after denervation or in some myopathies, indicating membrane irritability and active disease; they fire regularly and sound like ticking.

A fall in CMAP amplitude or area across a nerve segment with preserved distal response, indicating demyelination severe enough to halt impulse propagation; it causes weakness and may be focal.

A late motor response generated by antidromic activation of anterior horn cells and their recurrent discharge, used to assess proximal motor nerve segments and prolonged in demyelinating disease.

A monosynaptic reflex recorded from the soleus after submaximal tibial nerve stimulation, reflecting the S1 arc; prolonged latency suggests radiculopathy, plexopathy, or demyelinating neuropathy.

A test delivering trains of supramaximal stimuli to measure decrement of the CMAP, revealing postsynaptic junction defects such as myasthenia gravis or presynaptic facilitation in Lambert-Eaton syndrome.

Measurement of variability in the interval between two muscle fiber action potentials belonging to the same motor unit, reflecting neuromuscular transmission instability; increased jitter or blocking supports a junction disorder.