In patients with spinal muscular atrophy (SMA) headache after intrathecal administration of nusinersen is usually attributed to post-lumbar puncture syndrome. However, lumbar puncture opening pressure (LOP) has also been reported to be increased in children with SMA, both before and after treatment with nusinersen, although symptoms associated with increased LOP were not observed. We report to our knowledge the first case of symptomatic intracranial hypertension in an adult SMA patient. This 21-year-old man suffered from headache and vomiting followed by visual disturbances after the 12th injection of nusinersen. Bilateral papilledema was recognized ophthalmologically. MRI of the head showed signs of intracranial hypertension and additionally arachnoid cysts but not hydrocephalus. Symptoms resolved after 8 weeks of treatment with repeated lumbar punctures and acetazolamide. This case raises the possibility of intracranial hypertension as a complication of nusinersen therapy although arachnoid cysts represent another risk factor for intracranial hypertension. We recommend that patients suffering from headache after nusinersen injections should not only be questioned and examined for symptoms suggestive of post-lumbar puncture syndrome, but also intracranial hypertension.