Pseudomigraine is a term first introduced in 1983 to describe attacks of temporary neurologic deficit accompanied or followed by migrainous headache and cerebrospinal fluid (CSF) pleocytosis of unknown origin and automatic relief (10). Similar clinical presentations were reported previously under different names, such as migraine variants (1,13).

Fewer than 100 cases of HaNDL are reported in the literature (2,7), but it may be underdiagnosed as estimates of its annual incidence are up to 0.2 cases per 100,000 inhabitants (11). Contrary to migraine, this syndrome is more frequent in males (male:female ratio 2-3:1). Reported ages have ranged from 7 to 51 years, but most patients are around 30 years old (2,7,8).

The cause of HaNDL remains elusive. Proposed mechanisms are (11):

1. A rare variant of migraine with aura

2. Infectious meningoencephalitis

3. Autoimmunity

Episodes of HaNDL can be induced by cerebral angiography, which implicates a vascular etiopathology of the syndrome. The vascular theory of HaNDL is supported further by transcranial Doppler findings of asymmetrical changes in blood flow velocity and pulsatility index of middle cerebral artery (9). Alternatively, imaging studies suggest that neurologic deficits of HaDNL might be caused by cortical spreading depression (5,6), as in migraine with aura. Furthermore, overlap of clinical presentations between HaNDL and familial hemiplegic migraine triggered a search for mutations in the CACNA1A gene, which were not found (4). Finally, the CSF inflammatory picture of HaNDL suggests an inflammatory, autoimmune, or postinfectious etiology, and supportive data are awaited.

Diagnostic criteria (Revised International Classification for Headache Disorders [ICHD-II]) of HaNDL are listed in Table 115-1. The clinical characteristics of HaNDL are: (1) more than two discrete episodes of temporal focal neurologic (most often sensory plus aphasic) symptoms followed by moderate to severe headache and (2) complete and spontaneous relief of the condition after a few weeks or months. Characteristic paraclinical findings are: (1) CSF pleocytosis with lymphocytic predominance, whereas all serologic or CSF microbiologic studies are negative, and (2) ictal transient changes in brain single photon emission computed tomography (SPECT) and electroencephalogram (EEG) in the absence of any other abnormality in brain imaging (3,7). A combination of these clinical features and findings raises suspicion of HaNDL, but a 3-month follow-up period is necessary to establish the diagnosis, since the condition lasts from 6 hours to 49 days (mean ± SD = 14 ± 10 days, [7]).

Nonheadache clinical features of HaNDL include premonitory symptoms such as general malaise, cough, diarrhea, or rhinitis, which precede the clinical presentation by up to 3 weeks (11); symptoms of cortical dysfunction; and rarely symptoms of cerebellar or brainstem disturbance (Table 115-2).