Multifocal motor neuropathy presenting without conduction block and with fulminant respiratory failure: A case report

Abstract

Mr.P,a 38 year old gentleman presented with progressive weakness of left upper limb for 8 months,progressive weakness of right upper limb for 6 months,progressive thinning of both hands for 6 months and breathlessness on lying down for 4 months.There was no history of craniobulbar,sensory or autonomic symptoms.Family history was negative.On motor system examination,there was asymmetric distal predominant weakness of both upper limbs with wasting of intrinsic hand muscles bilaterally.Higher mental functions,cranial nerves and sensory system examination was normal.Routine hematological investigations,ANA profile,paraneoplastic profile&protein electrophoresis were unrewarding.ECG,2D ECHO,HRCT-Chest done i/v/o orthopnoea were normal.Ultrasound chest&abdomen showed sluggish movements of diaphragm bilaterally.Anti-MUSK antibody,RNS,Anti GM1 antibody were negative.Nerve conduction study showed asymmetric motor axonal neuropathy involving both upper limbs with no evidence of conduction block.Needle EMG was suggestive of acute and chronic denervation involving both upper limbs.MRI cervical spine with dynamic flexion was normal.A trial of steroids was considered and patient significantly worsened with severe respiratory distress,single-breath-count dropping from 25 to 3.A repeat bedside ultrasound showed complete paralysis of the right hemidiaphragm.IVIG was started at 2g/kg over 5 days following which patient's dyspnoea significantly improved to Single-Breath-Count of 30 over one week.I/V/O asymmetric pure motor neuropathy affecting both upper limbs,significantly worsening with steroids and promptly improving with IVIG,a diagnosis of Multifocal motor neuropathy was considered and patient was discharged to follow-up for monthly IVIG-pulses.Concluding,this case highlights the fact that multifocal motor neuropathy can present as an axonal variant without conduction blocks and respiratory failure can be one of the presenting complaints. NOTE:Patient/IRB approval taken