Trivial Degrees of Tonsillar Ectopia May be Symptomatic
Dan S. Heffez, M.D.; Jack D. Clemis, M.D.; Dean A. Elias, M.D.; Michael
A. Mikhael, M.D. and Leonard J. Cerullo, M.D.; Chicago, Illinois
OBJECTIVE: Cerebellar Tonsillar ectopia is considered
of clinical significance only when both tonsils are herniated at least
3mm below the foramen magnum. This criterion is too restrictive.
METHODS: We have evaluated 25 patients with symptoms
of cervicomedullary compression in whom the MRI scans showed less than
3mm of tonsillar ectopia. The most common complaints were headache (23/25),
nausea (19/25), vertigo (18/25), and gait instability (18/25). The duration
of symptoms ranged from 6 weeks to 11 years. Physical findings included
an intolerance of neck extension (21/25 patients), dysmetria (15/25),
positive Romberg sign (12/25) and occipital tenderness (11/13). The mean
tonsillar ectopia was only 0.49mm below the inferior rim of the foramen
magnum. Supplemental axial MRI images obtained through the plane of the
foramen magnum demonstrated crowding of the neuroanatomical structures
to advantage in every case.
RESULTS: One month following decompressive craniectomy
with or without duraplasty, 22/24 treated patients had shown an improvement
in all symptoms. One patient has refused treatment and 2 are still pending
follow-up. After a mean follow-up of 11.94 months, 7 patients remain asymptomatic,
14 patients are improved with resolution of neurological signs despite
some mild recurrent or residual symptoms, and 1 patient has severe dizziness.
CONCLUSION: We conclude that even minimal tonsillar
ectopia can be symptomatic and that surgical decompression of the foramen
magnum can be beneficial. The clinical significance of tonsillar ectopia
should be determined by the crowding of the contents of the foramen magnum
rather than simply by a measure of tonsillar descent.
Presented at 75 Years of Neurosurgery in Canada 1923-1998,
October 28-31, 1998, in Toronto, Ontario, Canada.