Neurosurgery 1992-98 February 1992, Volume 30, Number 2 246 Intraoperative Endomyelography during Syrinx Drainage: Technical Note Technical Note AUTHOR(S): Robertson, Daniel P., M.D.; Narayan, Raj K., M.D. Department of Neurosurgery, Baylor College of Medicine, Houston, Texas

caudally as possible; however, it is important to be able to confirm during surgery that the caudal drainage system will effectively drain the more cephalad portion of the syrinx. For this purpose, ultrasonography is limited by the extent of the laminectomy (16). We describe a technique of intraoperative puncture and contrast imaging of a posttraumatic cervicomedullary syrinx that allowed for cyst pressure measurements and the demonstration of the continuity of the syrinx cavity in a patient with progressive lower cranial nerve dysfunction.

ABSTRACT: There is no currently available noninvasive technique to ascertain with certainty the continuity of the cavity of a septated syrinx. A technique is described that allows the confirmation of the continuity before the surgical drainage of a syrinx. This technique may prevent the failure of the drainage because of septations and double cavities. Intraoperative endomyelography is simple to perform and requires no special equipment. Pressure measurements made before the injection of the contrast agent may provide insights into the pathogenesis of the syrinx and may be of prognostic and therapeutic significance. KEY WORDS: Endomyelography; Shunt; Syringomyelia Before the introduction of delayed metrizamide spinal computed tomographic (CT) scanning and magnetic resonance imaging (MRI), patients with syringomyelia were studied using gas myelography or a combination of iodinated contrast and gas, which documented spinal cord collapse with positional change (5,6,9,10,24). Communicating syrinxes also have been imaged via a lateral ventricular puncture or through ventriculoperitoneal shunts (8,22). In the planning of a shunting procedure, it is necessary to delineate the extent of the syrinx and the presence of any septa within it. Gas myelography does not provide this information. Delayed metrizamide CT scanning has been reported to overestimate the size and number of spinal cord cysts and may not show septa, which can present difficulties in shunt placement (16). With the technique of percutaneous endomyelography, water-soluble contrast material can be injected into a syrinx to determine its exact rostral-caudal extent. It is reported that syrinxes examined with this technique prove to be larger than predicted by noninvasive studies (3). Syrinx delineation using the percutaneous injection of metrizamide has been reported to be safe (14). Nevertheless, this procedure is associated with the risk of spinal cord injury and is used infrequently. MRI is helpful in studying cerebrospinal fluid (CSF) dynamics, aids in demonstrating the cause of a syrinx, and is now the imaging procedure of choice for pre- and postoperative syrinx evaluation (1); however, even MRI cannot establish conclusively the continuity of a syrinx cavity. In general, it is safest to drain the syrinx as

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TECHNIQUE A 22-year-old man suffered a C4-C5 subluxation with complete quadriplegia as a result of a motor vehicle accident in August 1988. Halo stabilization was used to achieve the fusion of C4-C5 over a period of 4 months. An MRI study of the cervicothoracic region revealed a spinal cord lucency at C4-C5 with a small syrinx inferiorly. In February 1990, the patient had a sudden onset of hypesthesia of the left side of his face and neck. A motor examination revealed spasticity in all limbs. An MRI study showed a syrinx extending from the medulla to the upper thoracic region (Fig. 1, A and B). Because of the high level of quadriplegia (C4), there was concern that the loss of even one segment of spinal cord function could precipitate respiratory failure. A laminectomy was performed at C6-C7 with the patient in a prone position. Intraoperative ultrasound was utilized to image the syrinx and showed septations. A Jelco (Critikon, Inc., Tampa, FL) catheter (20 gauge) connected to a saline-filled manometer was inserted into the cavity. Pressure readings zeroed at the patient's neck level revealed an intrasyrinx pressure of 12 cm of CSF, with ventilatory variation. Four milliliters of water-soluble contrast (Omnipaque 180, Winthrop Pharmaceuticals, New York, NY) were injected slowly into the syrinx after a portion of the syrinx fluid was drained. A lateral cervical x-ray showed that the cavity below the level of the injury at C4-C5 communicated with the syrinx in the medulla (Fig. 2). The contrast then was removed from the syrinx using gentle irrigation with saline. A fine Silastic shunt catheter was introduced into the syrinx and drained into the subarachnoid space. The shunt could thus be introduced at the C6C7 level with the assurance that the medullary syrinx would be drained. Two days postoperatively, the patient recovered sensation in his face and neck and had improvement in spasticity. Fifteen months after the shunt placement, the patient's recovery remained stable, and an MRI study of the cervical region showed the collapse of the medullary portion of the syrinx (Fig. 3).

DISCUSSION Percutaneous endomyelography was first performed by Westburg (24) and described by others (20) . The technique was performed using a spinal

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Neurosurgery 30; 246-248, 1992

Received for publication, February 7, 1991; accepted, final form, August 8, 1991. Reprint requests: Raj K. Narayan, M.D.,

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Department of Neurosurgery, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030. REFERENCES: (1-25) 1.

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needle with simultaneous gas myelography (11,19,24). The technique of syrinx puncture also has been helpful as a therapeutic measure (4,12,23,24). The simplicity of the use of eater-soluble contrast material for intraoperative myelography has been described (18,21). Iohexol is the nonionic, watersoluble contrast agent utilized in Omnipaque. Eightyeight percent of the intrathecally administered dose of iohexol is excreted by the kidneys within 24 hours without significant metabolism or protein binding. Contraindications to its use include known hypersensitivity to iohexol, active central nervous system (CNS) infection, history of food allergies, asthma, multiple myeloma, and sickle cell anemia. Intracranial or intraventricular exposure to this agent increases the risk of major motor seizures. Drugs that lower the seizure threshold (phenothiazines, monoamine oxidase inhibitors, CNS stimulants, tranquilizers, and major antidepressants) should be avoided 48 hours before and 24 hours after the use of intrathecally administered iohexol. Patients should be well hydrated with the head elevated during the intrathecal administration of iohexol. Aseptic meningitis occurs rarely (

Intraoperative endomyelography during syrinx drainage: technical note.

There is no currently available noninvasive technique to ascertain with certainty the continuity of the cavity of a septated syrinx. A technique is de...
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