A 14-year-old girl presented with a one-month history of progressive, ascending weakness in all four limbs, culminating in an inability to ambulate and increasing shortness of breath. Neurological examination revealed right-sided lower motor neuron facial weakness, 4/5 muscle strength in the upper extremities, and 2/5 in the lower extremities. Deep tendon reflexes were diminished. Nerve conduction studies demonstrated a severe axonal sensorimotor polyneuropathy with reduced compound muscle action potentials (CMAPs) and sensory nerve action potentials (SNAPs), consistent with axonal loss. Cerebrospinal fluid analysis revealed albuminocy to logic dissociation, with a protein level of 75 mg/dL and a normal cell count. Brain and spinal MRI were normal. The patient was diagnosed with acute motor and sensory axonal neuropathy (AMSAN), a variant of Guillain-Barré syndrome (GBS), and received a 5-day course of intravenous immunoglobulin (IVIG). She demonstrated gradual improvement and regained independent ambulation eventually. This case highlights the importance of considering GBS in the differential diagnosis of acute flaccid paralysis, even with atypical presentations like facial nerve palsy, and emphasizes the crucial role of electrodiagnostic studies and CSF analysis in confirming the diagnosis.