A Case of HaNDL with Low Cerebrospinal Fluid Level of Neurofilament Light Chain

Diagnosis of the syndrome of headache and neurological deficits with cerebrospinal fluid (CSF) lymphocytosis (HaNDL) is based on clinical features, and no diagnostic biomarkers are available. We present a case presenting with characteristic features of HaNDL and an MRI lesion in the splenium of corpus callosum. CSF neurofilament light chain (NFL) levels were assessed in this patient together with 7 additional HaNDL patients, 18 multiple sclerosis (MS) patients, and 15 primary headache patients. Both HaNDL and primary headache patients showed significantly lower NFL levels than MS patients. Our results suggest that increased CSF levels of NFL and neuroaxonal loss are not characteristic features of HaNDL. Neurological disorders mimicking HaNDL often present with increased levels of NFL, and thus CSF measurement of NFL might be useful in differential diagnosis of HaNDL.