Mutation Analysis of the CACNA1A Calcium Channel Subunit Gene in 27 Patients With Sporadic Hemiplegic Migraine FREE

FAMILIAL HEMIPLEGIC migraine (FHM) is a rare autosomal dominantly inherited subtype of migraine with aura.¹ Patients with FHM have attacks of migraine with aura that are also associated with hemiparesis. Otherwise, the symptoms of the headache and the aura phase are similar to those of nonhemiplegic migraine with aura, but may last much longer. At least 3 different genes have been implicated in FHM: the CACNA1A calcium subunit gene on chromosome 19p13 in half of the families with FHM,² an unknown gene on chromosome 1 in a few families, and at least a third one, as a few families could not be linked to either chromosome 19 or chromosome 1.^{3 - 4}

In sporadic hemiplegic migraine (SHM) (ie, hemiplegic migraine without a history of affected family members), the cause is unknown. In 2 of 3 patients with SHM who have cerebellar signs that have been analyzed for mutations in the CACNA1A gene, a mutation was found; a T666M mutation in a patient with SHM who had cerebellar ataxia, and a Y1384C mutation in a woman with mental retardion who had recurrent prolonged attacks of hemiplegic migraine, coma, and seizures associated with permanent cerebellar ataxia and atrophy.⁵ Eight patients with SHM who had no cerebellar signs were analyzed, but no mutation was found.^{6 - 8} In the present study we performed a mutation analysis of the coding exons of the CACNA1A gene by single-strand conformational polymorphism analysis in 27 patients with SHM.

As part of our ongoing mutation analysis of the CACNA1A gene, we studied 27 patients who had migraine with aura associated with hemiparesis. They originated from Western Europe, mostly the Netherlands, and one was from the United States. All available first-degree relatives were interviewed and their condition was diagnosed according to the criteria of the International Headache Society.¹ In all patients with SHM, polymerase chain reaction products of all 47 exons of the CACNA1A gene were screened for sequence aberrations by single-strand conformational polymorphism analysis.^{2 ,9}

Eight patients had no family member who had any type of migraine headache, while 19 patients had at least one first-degree relative who experienced migraine headache but none associated with hemiparesis (Table 1). Table 1 summarizes the clinical characteristics of the hemiplegic migraine attacks of the patients with SHM. The total duration of the migraine attacks varied between minutes and days, and even up to weeks in 2 patients. The paresis lasted between minutes and days, and weeks in 1 patient. In 2 patients the attacks fulfilled the criteria for basilar migraine.¹ Two patients reported loss of consciousness during attacks, 1 patient reported confusion, and 2 patients reported attacks triggered by minor head trauma. Mutation analysis of the CACNA1A gene was unremarkable in 25 patients. One patient carried a T666M mutation (family 27). This 78-year-old woman had migraine attacks with aphasia, pyrexia, hemianopsia, and hemiparesis starting at the age of 14 years. In between attacks the patient showed gaze-evoked horizontal nystagmus and upgazed paresis, dysarthria, and mild limb and gait ataxia; cerebral computed tomography revealed cerebellar atrophy. Another patient carried an R583Q mutation (patient 26). This 16-year-old boy had had 5 migraine attacks with aphasia, hemiparesis, and confusion with a duration of half an hour followed by headache. No cerebellar signs were present.

We found a CACNA1A mutation in 2 of 27 patients with SHM. These findings are consistent with the results of other smaller studies showing mutations in the CACNA1A gene in 2 of 3 patients with SHM who have permanent cerebellar ataxia, and no mutations in 8 patients without ataxia.^{6 - 8}

We used single-strand conformational polymorphism analysis, which is a reasonable sensitive (70%-90%) method for screening genes for point mutations as long as the fragments are not longer than 200 bases.¹⁰ However, other types of mutations like microdeletions or macrodeletions are undetectable by single-strand conformational polymorphism. To investigate this, other techniques such as Southern blotting and/or pulsed-field gel electrophoresis should be used. However, the genomic size of the CACNA1A gene, 350 kilobases, makes it hard to apply these alternative methods in a standard (and rapid) mutation screening. The promotor region or other regulatory elements were not analyzed, as at this moment, these have not been identified. Other studies in sporadic cases of specific genetic disorders give similar results as our study; a positive test rate is usually low, ranging from 2% to10%.¹¹

The patient in our study carrying the T666M mutation was distinctive from the others by showing permanent cerebellar ataxia and atrophy on computed tomographic scanning. Unfortunately, no DNA and direct information of the parents were available. The other mutation found in our study (R583Q), however, was found in a patient who did not have cerebellar symptoms. This R583Q mutation was reported previously in 4 families with FHM and associated ataxia.^{8 ,12} The mean age of onset of the ataxia is 40 years, ranging from 11 to 78 years.⁸ The patient with SHM in our study is only 16 years old; it is possible that he will develop these symptoms.

Clinical analysis of the symptoms of the aura in patients with FHM suggests an extensive overlap with basilar migraine.¹³ Only 2 of our patients with SHM had attacks fulfilling the criteria for basilar migraine. Unconsciousness during attacks and provocation of attacks by mild head trauma are not uncommon features of 19p13-linked families with FHM.^{14 - 15} In contrast, only 2 patients with SHM in this study reported these features. Thus, both genetic and clinical data suggest that FHM and SHM might be pathophysiologically different.

Accepted for publication January 7, 2002.

Author contributions: Study concept and design (Drs Terwindt, Haan, Frants, and Ferrari); acquisition of data (Drs Terwindt, Kors, van den Maagdenberg, and Ferrari and Mr Vermeulen); analysis and interpretation of data (Drs Terwindt, Kors, Haan, van den Maagdenberg, and Ferrari and Mr Vermeulen); drafting of the manuscript (Drs Terwindt, Kors, Haan and van den Maagdenberg and Mr Vermeulen); critical revision of the manuscript for important intellectual content (Drs Kors, Haan, van den Maagdenberg, Frants, and Ferrari); obtained funding (Drs Frants and Ferrari); administrative, technical, and material support (Dr van den Maagdenberg and Mr Vermeulen); study supervision (Drs Haan, van den Maagdenberg, Frants, and Ferrari).

This work was supported by nr 903-52-291 from the Netherlands Organization of Scientific Research, The Hague, and The Migraine Trust, London, England.

Members of the International Hemiplegic Migraine Research Group included the aforementioned authors and following persons: Neurologische Klinik der Ruhr-Universität, Bochum, Germany: J. Federlein, MD; Neurologische Universitätsklinik Regensburg, Regensburg, Germany: A. May, MD, PhD; Charing Cross Hospital, London, England: R. C. Peatfield, MD; Canisius Wilhelmina Hospital, Nymegen, the Netherlands: E. F. J. Poels, MD; Headache Center, Henry Ford Hospital and Health Sciences Center, Detroit, Mich: N. M. Ramadan, MD; Hospital de la Citadelle, Liège, Belgium: J. Schoenen, MD, PhD; Klinikum Grosshadern, München, Germany: A. Straube, MD, PhD; and Leeds, England: P. F. Taylor, MD.

Corresponding author: Michel Ferrari, MD, PhD, Department of Neurology, Leiden University Medical Centre, PO Box 9600, 2300 RC Leiden, the Netherlands (e-mail: M.D.Ferrari@lumc.nl).