Clinical phenotypes among patients with familial forms of Chiari malformation type 1

Chiari malformation type 1 (CM1) is the most common neurological disorder of the craniocervical junction. CM1 is characterized by cerebellar tonsillar herniation below the foramen magnum, causing CSF obstruction and neural compression. Patients with CM1 suffer from highly variable symptoms, progression, comorbidities, and outcomes, partly due to poor understanding of CM1 pathogenesis. In this paper, the authors present the only familial CM1 cohort study to statistically assess intrafamilial clinical phenotypes to date.

Comprehensive medical, surgical, and family histories and neuroimaging were collected from families with multiple CM1-affected family members. Univariate analysis was performed for each symptom, comorbidity, or surgery to compare observed versus expected frequencies of affected patients with another CM1-affected family member with the same clinical characteristic.

Twenty-four new familial CM1 cases (totaling 57 patients with CM1) are presented. Intrafamilial similarities were identified for age of onset, symptoms such as headaches (p = 0.007) and neck pain (p = 0.018), neurological comorbidities such as syringomyelia (p = 0.003) and hydrocephalus (p = 0.0001), neurodevelopmental conditions such as dyslexia (p < 0.0001), and connective tissue disorders (CTDs) such as Ehlers-Danlos syndrome (p < 0.0001).

These results suggest that CM1 and its associated clinical phenotypes, including age of onset, clinical symptoms, neurological comorbidities, neurodevelopmental conditions, and CTDs, are genetically influenced. Whole-exome sequencing of CM1 patient-parent trios has the potential to identify the genetic determinants of CM1, with implications for neurosurgical management.