Snapshot A 35-year-old man presents to the emergency department for difficulty with walking. His symptoms began approximately 1 week ago and has progressively worsened. He has noticed some lightheadedness with standing up from a seated position and some numbness in the bilateral lower extremities. Physical examination is notable for 4/5 power and decreased sensation to light touch and pinprick in the bilateral lower extremity and absent patellar and ankle reflexes. A lumbar puncture is performed, which demonstrates a cell count of 1/uL, protein is 135 mg/dL, and glucose is 65 mg/dL. He is admitted to the neurology floor for frequent negative inspiratory pressure and vital capacity measures and intravenous immunoglobulin. Introduction Definition an immune-mediated polyneuropathy that has many variant forms acute inflammatory demyelinating polyneuropathy chronic inflammatory demyelinating polyneuropathy Miller Fisher syndrome login to view 3 more bullets Epidemiology Risk factors recent infection Campylobacter jejuni login to view 1 more bullet Mycoplasma pneumoniae HIV Ebstein-Barr virus Zika virus Pathogenesis A previous infection triggers an immune response that cross-reacts with parts of the peripheral nerve via molecular mimicry damages the Schwann cells Presentation Symptoms/physical exam classic presentation typically ascending (and fairly symmetric) muscle weakness along depressed or absent reflexes other findings may include autonomic dysfunction peripheral cranial nerve palsies login to view 1 more bullet Miller Fisher variant ophthalmoplegia ataxia areflexia Imaging MRI indication typically used to rule out other causes of weakness findings in acute cases, may demonstrate enhancement and thickening of the login to view 2 more bullets Studies Spirometry to ensure adequate respiratory function intubate early if necessary Lumbar puncture albuminocytologic dissociation elevated protein normal white blood cell count Nerve conduction studies slowed conduction velocity reduced amplitude in compound muscle action potentials Differential Acute myelopathy differentiating factors spinal cord lesion on MRI Treatment Conservative acute supportive care indication login to view 7 more bullets Medical plasmapheresis indication login to view 1 more bullet intravenous immunoglobulin (IVIG) indication login to view 1 more bullet note that plasmapheresis and IVIG are equally effective Complications Respiratory failure Autonomic instability Complications from IVIG and plasmapheresis Prognosis Improved outcomes with either plasmapheresis or intravenous immunoglobulin