Today will be my fourth and final post on Chiari malformation.

While it is generally believed that Chiari malformation occurs at birth, recent scientific research has shown that this condition, which may be asymptomatic, can become symptomatic due to trauma. Also, there is a body of literature that recognizes that Chiari malformation may become acquired as opposed to congenital.

The leading study on the effects of trauma and Chiari malformation was published by Thomas H. Milhorat, M.D. et al in a study of 364 symptomatic patients.3 In this study, 364 symptomatic patients were evaluated (275 female and 89 male). The study found that Chiari malformation I is a disorder of the para-axial mesoderm that is characterized by underdevelopment of the posterior cranial fossa and overcrowding of the normally developed hindbrain. Clinical manifestations of Chiari malformation I were related to cerebrospinal fluid disturbances which were responsible for headaches, pseudo tumor-like episodes, endolymphatic hydrops, syringomyelia, hydrocephalus and direct compression of nervous tissue.

In this study, 25 percent of the patients cited trauma as the precipitating factor. The most common mechanisms were whiplash injuries and direct blows to the head and neck, which raised the possibility that certain types of trauma accentuate tonsillar impaction or result in subarachanoid hemorrhage that destabilizes a marginally compensated CSF system.

Dr. Milhorat and his colleagues can be located at North Shore University Hospital in Manhasset, New York.

This study is increasingly important as patients with traumatically symptomatic Chiari I malformation have found it exceedingly difficult to obtain reimbursement from their automobile insurance companies and find it difficult, in attempting to obtain compensation, to convince adjusters, judges and juries that a specific traumatic event was the cause of their symptomtology.

Giving weight to the argument that Chiari malformation may be acquired as well as simply congenital are various published studies. The reader is directed to the following published articles:

1. J Neurosurg 1995 Sep;83(3):556-558 Acquired Chiari malformation and syrin associated with bilateral chronic subdural hematoma. Case report. Morioka T, Sho Nishio S, Yoshida K, Hasuo K, Fukui M. Department of Neurosurgery, Kyushu University, Fukuoka, Japan.

2. J Neurosurg 1998 Feb;88(2):237-242 Acquired Chiari I malformation secondary to spontaneous spinal cerebrospinal fluid leakage and chronic intracranial hypotension syndrome in seven cases. Atkinson JL, Weinshenker BG, Miller GM, Piepgras DG, Mokri B. Department of Neurological Surgery, Mayo Clinic, Rochestert, Minnesota 55905.

3. Pediatr Neurosurg 1995;22(5):251-254 Acquired Chiari-I malformation and hydromyelia secondary to a giant craniopharyngio. Lee M, Rezai AR, Wisoff JH. Division of Pediatric Neurosurgery, New York University Medical Center, NY 10016.

4. “Acquired” Chiari I malformation. Case report. Huang PP, Constantini S. Department of Neurosurgery, New York University Medical Center, New York.

5. Acta Neurochir (Wien) 1998;140(5):417-27; discussion 427-8. The acquired Chiari malformation and syringomyelia following spinal CSF drainage: a incidence and management. Johnston I, Jacobson E, Besser M. Department of Neurosurgery, New Children’s Hospital, Australia.

6. A Case of a Temporary ACM/Syrinx, 28 year old female with a car accident head injury – when the injury healed the ACM/syrinx disappeared. Source – W.C. Clivero and D.H. Dinh, Neurology, v.30, #5, 758 (1992).4