↵a Four of these individuals had initially presented with headaches, and 1, with vertigo, all considered to be isolated issues without ongoing symptoms at the time of this review. All 3 individuals with Chiari malformations were included in the group lacking referable symptoms. Two additional patients had presented with trauma and were healthy after their other musculoskeletal injuries healed. Two more of these patients were evaluated for unilateral sensory hearing loss but were considered clinically healthy otherwise. An individual with a low-grade glial neoplasm had originally presented with a seizure but had no other symptoms after resection. One individual with multiple sclerosis had 2 episodes of lower extremity weakness and tingling that had resolved. The remaining patients lacking symptoms referable to the IHA had presenting symptoms that resolved with treatment or conservative measures (tongue hemihypertrophy with an arteriovascular malformation, scalp mass [sinus pericranii], Horner syndrome, lower extremity pain, and spasms).

↵b Born at 26–34 weeks' gestation.