HaNDL syndrome is a rare, self-limited disorder characterized by recurrent headaches, transient neurologic deficits, and cerebrospinal fluid (CSF) lymphocytosis. Typical manifestations include hemiparesis, hemiparesthesia, and aphasia. Seizures and behavioral changes are uncommon, posing a diagnostic challenge and often leading to extensive evaluation for infectious, autoimmune, or vascular etiologies. We report a case of a 35 year-old male patient with multiple episodes of headaches with a variety a focal neurological symptoms, including tonic-clonic seizures.

A 35-year-old man with a family history of migraine presented with recurrent episodes of severe headache accompanied by transient unilateral paresthesias, dysarthria, and later, confusion, agitation, and visual hallucinations. CSF analysis revealed lymphocytic pleocytosis with elevated protein and normal infectious and autoimmune studies. During hospitalization, he developed a bilateral tonic-clonic seizure with postictal focal weakness. Brain MRI and vascular imaging remained unremarkable; EEG demonstrated frontal intermittent rhythmic delta activity (FIRDA). Supportive management and discontinuation of empiric antivirals and antiepileptics were followed by clinical recovery. No further episodes occurred during 18 months of follow-up.

HaNDL syndrome should be considered in a patient with headaches, CSF lymphocytosis and unusual neurological findings (seizures, confusion, behavioral changes, abnormal EEG findings), when common and uncommon etiologies have been ruled out.