Background Guillain-Barré Syndrome (GBS) is a rare autoimmune disorder of the peripheral nervous system, classically characterized by symmetric, ascending muscle weakness that can progress to life-threatening respiratory depression. Diminished sensation, paresthesia, and autonomic dysfunction may also occur. GBS is a dysregulated immune response triggered by infections. 

Case Presentation A 15-year-old male with history of depression and substance use presented to the emergency room with one week of bilateral leg weakness, dyspnea, and migratory joint pains. One month prior, he had an upper respiratory infection which resolved spontaneously. Patient was travelling when he developed gait instability, dysarthria, photophobia, and shortness of breath. CT Head was normal. His respiratory function worsened, requiring escalating oxygen requirements, followed by acute deterioration of mental status. He was sedated, put on ventilatory support, and transferred to our critical care unit. 

Neurological exam revealed hypotonia, present reflexes, and poor muscle coordination out of proportion to muscle weakness, which initially suggested functional etiology. MRI and MRA brain and spine were unremarkable. Cerebral spinal fluid studies revealed albuminocytologic dissociation and elevated inflammatory markers (IL-6, IL-8). Potential autoimmune, paraneoplastic, rheumatologic, demyelinating, infectious, and toxic causes were ruled out. After unsuccessful extubation attempts, serial examination revealed involvement of cranial nerves VII, IX, and X.

He received a three-day course of intravenous immunoglobulin (2g daily) and gabapentin. Major complications included hospital acquired pneumonia and decompensated psychiatric state (worsening mood, panic attacks). Over three weeks, his mental status normalized, and he regained significant muscle strength and coordination. After confirming regained diaphragmatic function on ultrasound, he was extubated and weaned to room air. The patient was then transferred in stable condition to an acute rehabilitation center.

Discussion In pediatric patients, clinicians should conceptualize GBS as a spectrum of neurological symptoms that can differ from the typical ascending pattern but remain responsive to immunoglobulin treatment. This case proved unique because our patient’s history aligned with classic GBS, but he did not have expected radiological findings and patchy, rather than length-dependent, motor and sensory symptoms. His presentation had mixed features of multiple GBS subtypes, including Acute Motor Axonal Neuropathy and Multifocal Acquired Demyelinating Sensory and Motor Neuropathy. In addition to diaphragmatic weakness, patients can develop cranial neuropathies that prolong need for mechanical ventilation and increase risk of pneumonia. Lastly, in adolescents with prior psychiatric history, GBS can acutely exacerbate mood and anxiety symptoms which may be falsely attributed to functional neurological disorder.