• Abdul Aziz Khan
  • Sajid Nazir Bhatti
  • Ghayyur Khan
  • Ehtisham Ahmed
  • Ahsan Aurangzeb
  • Asghar Ali
  • Amjad Khan
  • Saleem Afzal


Background: The Chiari Malformation I (CMI) is a disorder of uncertain origin that has beentraditionally defined as downward herniation of the cerebellar tonsils through the foramen magnum.The anomaly is a leading cause of syringomyelia and occurs inassociation with osseus abnormalities atthe craniovertebral junction. In contrast to other Chiari malformations, CMI tends to present in thesecond or third decade of life and is sometimes referred to as the ‘adult-type’ Chiari malformation. Theobjective was to document clinical and radiological findings in Arnold Chiari Malformation-I.Method: This was a descriptive study carried out in Ayub Teaching Hospital Abbottabad atNeurosurgery Department during July 2008–July 2010. We examined a prospective cohort of 60symptomatic patients. All patients underwent magnetic resonance imaging of the head and spine.Results: There were 40 female and 20 male patients. The age of onset was 24.9±15.8 years. Commonassociated radiological problems included syringomyelia (60%), scoliosis (25%), andbasilarinvagination (12%), increased cervical lordosis 5 (8.5%), and Klippel Feil syndrome 2 (3.3%).The most consistent magnetic resonance imaging findings were obliteration of the retrocerebellarcerebrospinal fluid spaces (70% patients), tonsillar herniation of at least 5 mm (100% patients), andvarying degrees of post fossa anomalies. Linical manifestations were headaches, pseudotumor-likeepisodes, a Meniere’s disease-like syndrome, lower cranial nerve signs, and spinal cord disturbances inthe absence of syringomyelia. Conclusion: These data support accumulating evidence that CMI is adisorder of the para-axial mesoderm that is characterised by underdevelopment of the posterior cranialfossa and overcrowding of the normally developed hindbrain. Tonsillar herniation of less than 5 mmdoes not exclude the diagnosis. Clinical manifestations of CMI seem to be related to cerebrospinal fluiddisturbances (which are responsible for headaches, pseudotumor-like episodes, endolymphatic hydrops,syringomyelia, and hydrocephalus) and direct compression of nervous tissue.Keywords: Arnold Chiari Malformation, Posterior cranial fossa, Cerebrospinal fluid


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