506 - Acute Motor Axonal Neuropathy (AMAN) with Rapid Functional Decline: Diagnostic and Therapeutic Insights

Case Diagnosis:
Case Diagnosis: Acute Motor Axonal Neuropathy (AMAN) - A Variant of Guillain-Barré Syndrome (GBS)


Case Description:
A 70-year-old male presented to the emergency department with worsening bilateral upper extremity weakness that began earlier that morning. He had experienced severe diarrhea one week prior. Neurological examination revealed weakness in finger and wrist extension, but cranial nerves, sensation, and reflexes were intact. No muscle atrophy, rigidity, or spasticity noted. Gait and station were normal. Brain MRI was negative for acute ischemia and cervical spine MRI showed no abnormal focal enhancements.



By the following morning, the patient’s condition deteriorated to functional quadriplegia. He developed urinary retention, shallow tachypnea, hypophonia, and absent reflexes throughout. Intubation was required due to respiratory failure. Sensory examination remained normal. Cerebrospinal fluid (CSF) analysis showed elevated protein levels with a normal white blood cell count. Positive serum C. jejuni IgG and anti-GM1 antibodies supported the diagnosis of AMAN. The patient underwent plasmapheresis (PLEX) and intravenous immunoglobulin (IVIG) with minimal improvement over the subsequent weeks.


Discussions: AMAN is a variant of Guillain-Barré Syndrome marked by acute motor weakness without sensory involvement, accounting for about 5% of GBS cases in North America and Europe. Diagnosing AMAN can be challenging due to its variable symptoms and atypical presentations. Electrophysiological studies and specific antibody detection are crucial for accurate diagnosis. Patients with axonal forms of GBS like AMAN face a significantly higher risk of long-term disability. Despite relatively early detection and treatment with IVIG and PLEX, the patient has experienced persistent flaccid paralysis, with only slight improvement in bilateral lower extremity function one year later.

Conclusions: The increased risk of long-term disability in AMAN underscores the need for an interdisciplinary management approach. Collaboration among neurologists, physiatrists, physical therapists, and other healthcare professionals is essential for optimizing patient outcomes.