Chiari drop attacks: surgical decompression and the role of tilt table testing

Chiari I malformation (CM1) is characterized by impaired CSF flow through the foramen magnum. Dysfunctional autonomic cardiovascular regulation may result in syncope. Syncope may be the primary presenting symptom of CM1: a syndrome termed Chiari drop attack. It has been postulated that Chiari drop attack is secondary to dysautonomia caused by hindbrain compression. There has been recent debate regarding the association between CM1, dysautonomia and Chiari drop attack.

We selected patients with Chiari drop attacks who had negative workups for cardiac syncope, followed by tilt table testing and subsequent surgical decompression. We report test results and clinical outcomes following CM1 decompression.

Ten patients met the inclusion criteria: 5 patients had positive and 5 negative tilt table tests. Following decompression, 7 had symptomatic improvement or resolution and 3 failed to improve. The sensitivity and specificity of the tilt table test for detecting clinical improvement with surgical decompression was 43 and 33%, respectively. Tilt table testing had 40% accuracy in predicting clinical response to decompression.

In this short series, surgical decompression of CM1 has a high success rate (70%) for patients with Chiari drop attacks. Tilt table testing has poor predictive value in judging the clinical response to surgical decompression and is not a useful test to guide surgical decision- making.