Treatment-Related Fluctuation in Guillain-Barre Syndrome With the Acute Motor-Sensory Axonal Neuropathy (AMSAN) Variant: A Case Report.

We present the case of a 60-year-old male patient with Guillain-Barré syndrome (GBS) who experienced treatment-related fluctuations (TRF) with a history of ayahuasca consumption. The patient presented to the neurological emergency department without a history of infection (upper respiratory tract or diarrhea) or vaccination in the past four weeks, but 14 days prior, the patient had consumed ayahuasca. Upon admission, the patient exhibited progressive weakness in all four limbs, with no cranial nerve involvement, a muscle strength Medical Research Council (MRC) score of 36/60, and generalized areflexia. Cerebrospinal fluid analysis showed slightly elevated protein levels at 50 mg/dL and a cell count of 2 (lumbar puncture was performed three days after the onset of symptoms). Neurophysiological studies met the criteria for the acute motor-sensory axonal neuropathy (AMSAN) variant. A diagnosis of GBS was established, Brighton criteria grade 1. The patient received treatment with intravenous human immunoglobulin, resulting in improvement with an MRC score of 48/60 at discharge. However, on day 10, he returned with worsening muscle strength (MRC score of 20/60), necessitating ventilatory support. TRF was considered, and retreatment with human immunoglobulin was initiated.