Sonographic localization of a nonpalpable shunt: Ultrasound-assisted ventricular shunt tap
A 53-year-old male with a past medical history significant for hypertension, noninsulin-dependent diabetes mellitus, alcohol abuse, seizures, and traumatic brain injury secondary to a fall, necessitating several decompressive craniectomies, bilateral cranioplasties and a left occipital ventriculoperitoneal (VP) shunt (Rickham reservoir), initially presented to an outside institution obtunded and in acute status epilepticus. Seizures were initially generalized tonic-clonic, and then later right-sided convulsions with eye deviation. His seizures were aborted with intravenous lorazepam and fosphenytoin. A head CT was obtained at that time that was suggestive of hydrocephalus, which prompted transfer to our facility.\nUpon arrival to our ED the patient was noted to have residual focal right arm and facial twitching, for which he was reloaded with antiepileptic agents. The patient was new to our institution, and no prior imaging was available to aid in determining if he had acute hydrocephalus. A shunt series obtained in the ED showed no signs of discontinuity throughout the shunt system. Therefore, we attempted to perform a VP shunt tap to assess intracranial pressure and determine if he had either proximal or distal shunt failure. Initially, on examination his shunt reservoir was not palpable. This was likely secondary to the large thickness of his scalp and the location of his Rickham reservoir near a burr hole cover and along a raised ridge from his left cranioplasty site [].\nWe utilized the ED's portable ultrasound machine (Edge ® model; SonoSite, Incorporated), typically used in the ED for other procedures, to quickly assist us with imaging through the scalp. Using a 6 cm, 13-6 MHz linear transducer, visualization in both the short-axis and long-axis views allowed for a thorough examination and confirmation of the exact placement of the Rickham reservoir []. The patient was then prepped in the standard fashion, with the Rickham site marked and outlined allowing for the easy placement of our 23-guage butterfly needle into the reservoir site []. Once in place, there was no spontaneous flow. Utilizing a 5-cc syringe, we were only able to obtain a few drops of residual fluid initially from the proximal catheter with 2-3 mL of negative back pressure, and then no CSF return at all. The result of our ventricular shunt tap suggested proximal shunt failure. The patient was then emergently taken to the operating room (OR) for a shunt revision. In the OR, the left occipital proximal shunt catheter was found to be obstructed, demonstrating shunt failure, which correlated with our shunt tap. In this setting, the decision was made to place a left frontal VP shunt in the standard fashion. Briefly, an incision was made over Kocher's point and a burr hole was placed using a perforator drill. The left frontal catheter was then passed to the appropriate depth and clear CSF return was visualized under high pressure. The distal catheter was then tunneled from the frontal scalp incision to the back part of the previous trauma craniotomy incision, then down towards the neck. The sites were joined with a straight connector along with a medium-low pressure valve. Prior to the connection, distal runoff was checked and found to be appropriate. Postoperatively, the patient did well and was eventually transferred back to his nursing facility.