Guillain-Barré syndrome (GBS) classically manifests as an acute ascending paralysis with hypo or areflexia, the involvement of the brainstem, is infrequent. We present a 75-year-old woman with rapidly progressive quadriparesis that progressed within hours to respiratory insufficiency and coma, with absence of the corneal, nauseous and oculocephalic reflexes. The brain magnetic resonance was normal and the electroencephalogram showed the presence of brain activity. Given the clinical suspicion of GBS, she received two courses of intravenous immunoglobulin, presenting improvement with recovery of blinking, spontaneous eye opening and response to simple commands based on eye movements. Electromyography showed acute motor axonal neuropathy and the lumbar puncture showed albumin-cytological dissociation, which confirmed the diagnosis of GBS. The patient tolerated withdrawal of mechanical ventilation 3 months later and was discharged after 5 months with a Hughes disability scale of 4. This case shows that there are severe and rapidly progressive forms of GBS that can compromise the brainstem, which can manifest as disorder of consciousness and alteration of truncal reflexes, imitating brain death.