Thermography - a valuable tool to test hydrocephalus shunt patency.

Introduction: Shunt-function in hydrocephalic patients is verified by clinical examination and repeated cranial computed tomography (CCT) in most cases. Because of the disadvantages of multiple radiation especially in children it was our aim to introduce video-thermography as a simple and non-invasive methodology to evaluate shunt function.

Methods: 54 patients treated with shunts for hydrocephalus were tested. A ventriculo-peritoneal shunt had been implanted in 38 patients, a ventriculo-atrial shunt in 16 patients. Recent CCT-scans were available for all patients and served as control. None of the patients presented with clinical signs of shunt-dysfunction. The temperature of the skin covering the drainage catheter distal to the valve was recorded real-time by a calibrated infrared camera. After cooling the skin area downstream of the valve for exactly 1 min with an ice pack, changes of the skin temperature in the area downstream were registered by a thermocamera. The signals were transferred to a video screen and recorded on videotape. By off-line analysis of the obtained pseudo colour images variations of 0.1 degrees C in skin temperature could be measured.

Results: Temperature distribution of the area under investigation revealed a significant reduction of the skin temperature according to the location of the downstream catheter segment in 48 patients after cooling. In 6 patients skin temperature remained constant, although clinical evaluation and CCT-scan showed no signs of shunt dysfunction. Shunt patency could be verified in more than 85% of the patients by thermal imaging.

Conclusion: Infrared-thermography is a valuable and promising tool for replacing CCT-scanning as a screening method to test shunt function in hydrocephalic patients.