Diffusion restriction in the splenium of the corpus callosum in a patient with the syndrome of transient headache with neurological deficits and CSF lymphocytosis (HaNDL): a challenge to the diagnostic criteria?

The diagnosis of transient headache with neurological deficits and CSF lymphocytosis (HaNDL) is essentially based on the clinical and CSF findings, and the absence of MRI abnormalities. We present a young man with the clinical characteristics of HaNDL, but also an area of diffusion restriction in the splenium of the corpus callosum (SCC). When considering the limited experience with this MRI technique in this disorder, we wonder if a normal MRI can be maintained as an indispensable criterion for diagnosis. Similar MRI abnormalities limited to the SCC have been found in mild forms of meningoencephalitis, but their origin remains obscure. In at least some cases not only a clinical, but also a radiological overlap could exist between both disorders.