Trivial head trauma may be complicated by severe, sometimes even fatal, cerebral edema and coma occurring after a lucid interval ("delayed cerebral edema"). Attacks of familial hemiplegic migraine (FHM) can be triggered by minor head trauma and are sometimes accompanied by coma. Mutations in the CACNA1A calcium channel subunit gene on chromosome 19 are associated with a wide spectrum of mutation-specific episodic and chronic neurological disorders, including FHM with or without coma. We investigated the role of the CACNA1A gene in three subjects with delayed cerebral edema. Two subjects originated from a family with extreme FHM, and one subject was the previously asymptomatic daughter of a sporadic patient with hemiplegic migraine attacks. In all three subjects with delayed severe edema, we found a C-to-T substitution resulting in the substitution of serine for lysine at codon 218 (S218L) in the CACNA1A gene. The mutation was absent in nonaffected family members and 152 control individuals. Haplotype analysis excluded a common founder for both families. Neuropathological examination in one subject showed Purkinje cell loss with relative preservation of granule cells and sparing of the dentate and inferior olivary nuclei. We conclude that the novel S218L mutation in the CACNA1A calcium channel subunit gene is involved in FHM and delayed fatal cerebral edema and coma after minor head trauma. This finding may have important implications for the understanding and treatment of this dramatic syndrome.

Arch Neurol. 2002 Jun;59(6):1016‐1018 Background: Familial hemiplegic migraine is a rare autosomal dominant subtype of migraine with aura that in half of the families is caused by mutations in the CACNA1A gene on chromosome 19p13. In sporadic hemiplegic migraine (SHM), that is, hemiplegic migraine without affected family members, the contribution of the CACNA1A gene is unknown. Objective: To investigate the involvement of the CACNA1A calcium channel subunit gene in SHM. Methods: We screened 27 patients with SHM for mutations in the CACNA1A gene by a combination of single‐strand conformational polymorphism analysis and sequence analysis. Results: One patient with SHM also had ataxia, nystagmus, and cerebellar atrophy on computed tomography and carried a T666M mutation. Another patient with SHM who had no cerebellar signs carried an R583Q mutation. No mutations or interictal neurological abnormalities were found in the remaining 25 patients with SHM. Conclusions: Most patients with SHM do not have a CACNA1A mutation. The results of this study, combined with the findings reported in the literature, show that the presence of cerebellar symptoms in addition to the hemiplegic attacks increases the chance of finding a CACNA1A mutation. In addition, to our knowledge, we have found a first patient with SHM without cerebellar signs with a mutation. Comment: The story on calcium channelopathies and neurologic disorders becomes ever more complex, as multiple neurologic disorders appear linked to varying forms of calcium‐channel mutations. Professor Ferrari has described links to cerebellar disorders, to a peculiar and severe response to head trauma, and to epilepsy, as well as to familial hemiplegic migraine. Now his group finds that the most frequently found calcium channelopathy mutations are not found in most patients with spontaneous hemiplegic migraine. Does this just mean that other mutations, not yet described, cause a common phenotypic expression? Or are there multiple causes for the hemiplegic migraine syndrome, and not all of them due to calcium channelopathies? SJT

Most patients with SHM do not have a CACNA1A mutation. The results of this study, combined with the findings reported in the literature, show that the presence of cerebellar symptoms in addition to the hemiplegic attacks increases the chance of finding a CACNA1A mutation. In addition, to our knowledge, we have found a first patient with SHM without cerebellar signs with a mutation.

In this family with autosomal dominant FCTE, specific clinical and electrophysiological features were identified. Exclusion of linkage to chromosome 8q23.3-q24.1 indicates that genetic heterogeneity exists for FCTE.

We analysed the CACNA1A gene, located on chromosome 19p13, in three unrelated families and one sporadic case with episodic ataxia type 2 (EA-2). In two of the families and the sporadic patient, novel truncating mutations, which disrupt the reading frame and result in a premature stop of the CACNA1A protein, were identified in exons 14, 16 and 26. In the remaining family, a novel missense mutation (H253Y) was found. Of the twenty two EA-2 mutations identified thus far, including those of the present study, seventeen are truncating mutations and five are missense mutations, all resulting in an EA-2 clinical phenotype.