A 32-year-old man with a residual spastic quadriparesis from a traumatic C5-C6 fracture experienced a severe thunderclap headache. The medical history revealed an episode of autonomic dysreflexia (AD) due to neurogenic bladder/urinary tract infection (UTI). Blood pressure monitoring at admission revealed hypertension; blood pressure reaching 160/100 mmHg (average blood pressure in these patients and also in this patient being 90/60 mmHg). CT scan of the head, cerebrospinal fluid examination, CT angiography and MR angiography of the brain vessels were normal. Another UTI and a subsequent spell of AD were diagnosed. The patient continued to experience recurrent thunderclap headaches. Selective catheter cerebral angiography revealed multiple calibre changes in the intracranial blood vessels. A diagnosis of reversible cerebral vasoconstriction syndrome (RCVS) due to AD was considered. A magnetic resonance imaging (MRI) of the brain after 2 weeks revealed ischaemic changes in the left hemisphere. Follow-up brain MRI after 3 weeks showed reduction in size of the ischaemic changes, and catheter angiography after 6 weeks demonstrated improvement/normalization. A diagnosis of RCVS could be established. Repeated MRI/CT of the brain after 6 months demonstrated a large infarction in the left hemisphere. RCVS has been reported to occur in various clinical settings. It can occur in the setting of AD in patients with traumatic cervical cord injury. Prompt recognition of RCVS may be of vital importance to avoid further morbidity in patients with spinal cord injury.