INTRODUCTION AND DEFINITION
The syndrome of transient headache and neurologic deficits with cerebrospinal fluid lymphocytosis (HaNDL) is a self-limited, benign entity that was first clearly characterized in 1981 , when it was called a migrainous syndrome with cerebrospinal fluid (CSF) pleocytosis. It was given its current name in 1995 , and has also been referred to as pseudomigraine with temporary neurologic symptoms and lymphocytic pleocytosis (PMP syndrome) . As the name implies, HaNDL is characterized by one or more episodes of severe headache, transient neurologic deficits, and lymphocytic pleocytosis in the CSF.
The precise etiology of HaNDL is not yet fully understood. Though some initially speculated that the syndrome represented a severe migraine [4,5], others favored an inflammatory or infectious origin, given the CSF lymphocytosis, frequent viral prodrome, and monophasic course [1,2]. However, despite extensive viral serological evaluation, there are few reports confirming a viral association. In one early case, echovirus 30 was isolated using cell tissue cultures from a patient with an illness resembling HaNDL . In another case of HaNDL, serologic evidence of human herpesvirus 6 infection was detected by an elevated titer of IgM at presentation that gradually decreased to normal range by four weeks after admission .
Findings on single-photon emission computed tomography (SPECT), perfusion imaging with CT and MRI, transcranial Doppler, and electrophysiology studies of patients with HaNDL are suggestive of a migrainous pathophysiology:
●SPECT studies have demonstrated focal or widespread areas of decreased blood flow on the side of origin of the neurologic deficits [8-11], suggestive of the spreading depression-like mechanism similar to that proposed for migraine.
●Head CT perfusion scan showed decreased and delayed perfusion involving an entire hemisphere in a patient with HaNDL , while MRI perfusion-weighted imaging showed focal parieto-occipital hypoperfusion involving another patient with HaNDL . In both cases, areas of reduced perfusion correlated with the neurologic deficits.