Acute Motor Sensory Axonal Neuropathy (AMSAN) in a Pediatric Patient: Case Report

Case Diagnosis: Acute Motor Sensory Axonal Neuropathy (AMSAN), a variant of Guillain-Barré Syndrome (GBS)

Case Description or Program Description: An 11-year-old male developed ascending weakness with numbness and areflexia after strep pharyngitis. In a span of 1-3 days since the onset, his symptoms worsened with tetraparesis along with significant neuropathic pain and respiratory failure requiring intubation. Based on his presentation with elevated protein in cerebrospinal fluid, normal MRI brain and entire spine, and results of electrodiagnostic study (no measurable response of SNAP or CMAP of median, ulnar, tibial, and fibular nerves), he was diagnosed with acute motor sensory axonal neuropathy (AMSAN) and was treated with the Zipper methods (plasmapheresis followed by intravenous immunoglobulin). After 1.5 months of medical stabilization at an acute care facility, he was admitted to an intensive rehab hospital. Upon admission to rehab, he had significant tetraparesis, lower limbs affected more severely than upper limbs, areflexia, dysphagia, neurogenic bowel/bladder, and neuropathic pain with initial WeeFIM score of 39, being mostly dependent for mobility and ADLs. Although his electrodiagnostic results and presentations are associated with a poorer prognosis, after 2 months of inpatient multidisciplinary rehab team, he was discharged home at supervision level with WeeFIM score of 104.

Setting: Tertiary care pediatric hospital

Assessment/Results: Our patient developed a rapid onset ascending weakness, numbness, areflexia, and associated medical conditions after strep pharyngitis with workups indicative of AMSAN. Although his case was thought to have poor outcome, he made great function gains after 2 months of inpatient rehab hospitalization.

Discussion (relevance): AMSAN is considered the most severe variant of GBS with an incidence rate of 3-5 cases per 10,000,000, accounting for < 5% of all GBS cases. It is known for its fast progression that often leads to tetraparesis within 1 week after symptom onset. The prognosis of AMSAN is generally less favorable than GBS with its slow and incomplete recovery, but with an aggressive multidisciplinary rehab team approach, good outcomes can be achieved.

Conclusions: It is important for clinicians to recognize clinical manifestations of AMSAN and be aware of its rapid progression and slow, prolonged recovery as it can provide resources and counseling to rehab team, patients, and their families.