Abstract Details

Title Mechanism of Arachnoid Cyst Formation Identified by Positional Headache

Topic Headache

Presentation(s) P01 - (-)

Poster/Presentation
Number 090

Objective

Background There are theories behind the formation of arachnoid cysts, such as hypersecretion by cells in the cystic wall, a ball-valve mechanism, and fluid influx due to a pressure gradient. Headache is the most common presenting symptom. The headache caused by increased intracranial pressure is classically characterized by position, worsening when laying down and improving on sitting up or standing. This case provides evidence that the ball- valve effect of a cystic structure causes fluid entrapment and expansion and also that it is an important cause of positional headaches.

Design/Methods A 16 year old female with a history of migraine, presented to the hospital with increasing severity and frequency of her headaches and vomiting. Unlike her usual headaches, these worsened when lying flat and improved in an upright position. Over the counter analgesics provided no relief. Her exam showed no evidence of papilledema on fundoscopic exam. An MRI Brain showed a 6.1 x 3.8 cm retrocerebellar arachnoid cyst with mass effect on the cerebellar vermis. She underwent a posterior fossa craniotomy and fenestration of the cyst. A ball-valve mechanism was visualized which showed a small opening from the lower margin of the arachnoid cyst into the spinal compartment which could account for her positional headache.

Results After fenestration of the arachnoid cyst, the patient's headache improved and she was discharged home.

Conclusions One of the theories behind cyst formation is entrapment of cerebrospinal fluid by a one way/ball-valve mechanism. This case provides a compelling argument that the ball-valve mechanism is the cause for cyst formation and enlargement. Clinically, it may be identified by the presence of a positional headache.

Authors/Disclosures
Deena Kuruvilla, MD (Westport Headache Institute) PRESENTER	Dr. Kuruvilla has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Pfizer. Dr. Kuruvilla has received personal compensation in the range of $10,000-$49,999 for serving on a Speakers Bureau for Abbvie. Dr. Kuruvilla has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Abbvie/Allergan. Dr. Kuruvilla has received personal compensation in the range of $10,000-$49,999 for serving as an Expert Witness for HPMB.
Shilpa Haldal, MD	Dr. Haldal has nothing to disclose.
John Gaitanis, MD	No disclosure on file
	No disclosure on file
	No disclosure on file

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