Chiari malformation type 1.5 as a cause of chronic occipital headache in an adult: a case report

Abstract

Case Presentation: A 38-year-old man sought specialized care presenting with a chronic occipital headache, compressive in nature, with marked exacerbation during Valsalva maneuvers, coughing, and physical exertion. The clinical presentation was accompanied by cervicalgia and upper limb paresthesia, with no prior history of known neurological disorders. Neurological examination revealed sensory impairment in the right upper limb and reduced grip strength. Based on the clinical presentation, brain magnetic resonance imaging focusing on the craniocervical junction was requested and demonstrated a 12-mm herniation of the cerebellar tonsils below the foramen magnum, associated with an inferior displacement of the obex, findings consistent with Chiari malformation type 1.5. Mild dilation of the supratentorial ventricular system was observed, without signs of cerebrospinal fluid transudation. Cervical spine magnetic resonance imaging ruled out associated syringomyelia. Initial management followed a conservative approach focused on pain control, resulting in substantial clinical improvement and postponement of surgical decompression. Discussion: Chiari malformation type I and its more complex variant, Chiari malformation type 1.5, are frequently underdiagnosed in adults due to their polymorphic clinical presentation, which may mimic primary headaches or vestibular disorders. In the reported case, the "exertional headache" served as the main clinical marker prompting further investigation, which revealed not only tonsillar herniation but also the inferior displacement of the obex, a finding that defines type 1.5 and suggests a more pronounced impairment of cerebrospinal fluid flow, explaining the patient’s compressive symptoms. Although structural magnetic resonance imaging remains the gold standard for diagnostic confirmation, recent research on Chiari malformation suggests that the diagnostic approach should evolve from static morphometry to the analysis of cerebrospinal fluid flow dynamics via phase-contrast magnetic resonance imaging. This approach allows precise identification of the functional impact of posterior fossa disproportion, supporting individualized therapeutic decisions that balance the severity of compression with the patient's functional status. Final Comments: This report underscores the importance of recognizing atypical headache symptoms in neurological practice, where accurate neuroimaging diagnosis is crucial to prevent irreversible structural damage, such as syringomyelia. Looking toward the future of neurology, the integration of advanced imaging technologies and the use of clinical decision-support tools are considered foundations for favorable and personalized outcomes. It is concluded that a rigorous correlation between semiology and imaging findings, coupled with longitudinal clinical surveillance, ensures therapeutic success and the preservation of functionality and quality of life in adult patients with Chiari malformation.