Abstracts

Rationale: The clinical symptoms and complications post subdural strip implantation for invasive electrographic recording are well documented in the literature. Some subdural strip locations are associated with more morbidity than others. Localized dural referred pain is an uncommon pain syndrome post subdural strip implantation; however this type of pain is usually intractable to the commonly used analgesic agents. Methods: A subset of 9 out of 41 adult patients who underwent subdural strip implantations in our institution during the period from June 2007 to May 2008 were identified to have periorbital pain in a prospective analysis. The locations of the subdural strips were confirmed by CT/MRI superimposition. The pain map, intensity scale and characteristics of the pain were analyzed, as well as the factors associated with the development of this unique pain syndrome. Results: All 9 patients developed a similar pain, described as a throbbing pain localized to the periorbital region, with no associated sensory symptomatology. This particular pain location appears to follow the trigeminal nerve ophthalmic division distribution. The pain intensity ranged between 8 and 10 on a 10 point analog pain scale in all patients. This pain syndrome was intractable to the usual analgesic agents. In 8 patients the pain was controlled by supraorbital-supratrochlear nerve blockade using a mixture of xylocaine and bupivicaine. Two patients received two blockade sessions. Electrodes located at the junction of the tentorium and falx cerebri covering mesial occipital and inferior occipitotemporal surfaces were most commonly responsible for this pain syndrome. Conclusions: We describe a medically intractable unique pain syndrome related to subdural strip implantation at the junction of tentorium and falx cerebri. The pathophysiology of this pain remains unclear, however, it may be caused by dural irritation by the subdural strip which might cause trigeminal nerve hypersensitivity. Further investigations to identify the exact mechanism of this pain syndrome are required.