Multifocal motor neuropathy with conduction block: a case report

Abstract

Introduction: Multifocal motor neuropathy with conduction block (MMN-BC) is a rare disease and a distinct entity, its clinical and electrophysiological features differ from other chronic inflammatory demyelinating neuropathies. Its’ first description in 1988 lead to new diagnosing assessments. The distinction of this disease is very important as the treatment differs and incorrect treatment can lead to clinical decline. Clinical case: We report a case of a 62-year old man who developed muscular weakness in all his four limbs, muscle wasting of both hands (2005), claudication, difficulty ascending stairs, muscularcramps, palpebral ptosis(2007) on the right eye and diplopia on upward gaze. No other neurological signs detected. His past medical history included: Amygdalectomy (1985), Hearnia repair(1995), Chronic pancreatitis. Results: At first radial compresive neuropathy was suspected, after exclusion of this diagnose Myastenia gravis the ocular form was suspected. Anti-AchR antibodies were not detected and anticholinesterase drugs did not show effect. Electroneurography revealed conduction block on the right medianus nerve, decrease of sensory nerve action potentials (SNAP) on the medianus and ulnaris nerves bilaterally. Compound muscle action potentials (CMAP) decrease on the left nervus peroneus profundus. CMAP decrease on the fibers of nervus tibialis posterior bilaterally. Also alfa waves were detected on the fibers of nervus tibialis posterior bilaterally and latency increase of F waves. Imunological assay has revealed anti-GM1 and anti-GD1b positive antibodies. The patient was diagnosed with Multifocal Motor Neuropathy with Conduction Block with flaccid tetraparesis with oculomotor nerve implication. The patient underwent intravenous immunoglobulin (IVIG) and cyclophosphamide therapy with prominent improvement in muscle force and other clinical features. Conclusions: Slow onset of assymetrical limb weakness, sometimes with visible muscle wasting and fasciculations without any sensory abnormalities should guide the physician to consider MMN-CB and its’ chronic immune mediated demyelinating course. As this disease is extremely rare we highlight the importance of this case report to raise awareness on MMN-CB. This condition is often misdiagnosed at Primary Health Centers and this case shows that time efficient diagnose and corect treatment can improve the clinical and electrophysiological indicators.