Résumé :
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Communication n° 360 SUMMARY: Acute motor axonal neuropathies (AMAN) have been recently individualised as a specific entity in patients presenting with Guillain Barré syndrome. In the literature, very few pediatric cases have been so far described. We report the case of a twelve year old child who presented, ten days after an acute episode of diarrhea, acute flaccid monoparesis of the left lower limb with abolition of the left knee reflexe. The child never presented sensitive manifestations. Investigations performed on the sixth day after the onset of the monoparesis did not show any abnormalities: no inflammation on blood tests, normal cerebrospinal fluid , normal brain and spine magnetic resonance imaging (MRI). Neurophysiological study (electromyogram, motor and sensitive nerve conductions) was normal. Evolution was marked by rapid onset of proximal amyotrophy at the lower left limb level. Muscle MRI was then performed and showed diffuse and non selective amyotrophy of the left thigh. Neurophysiological studies were repeated 10 days after the first evaluation and showed reduced amplitude of the peripheral motor action potentials with normal nerve conduction velocities in all four limbs,suggesting the diagnosis of AMAN. Further studies showed elevated serum mycoplasma pneumoniae titers ( IgG:590UI/ml and IgM:1387UI/ml). This observation is remarkable because of the atypical clinical presentation.It also confirms that neurophysiological data typical of AMAN may be delayed. The diagnosis of AMAN should be evoked in case of acute proximal amyotrophic monoparesis, even when the initial neurophysiology is normal.
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