Ultrasound determination of cerebrospinal fluid shunt patency Technical note
MARC A. FLITTER, M.D., WILLIAM A. BUCHHEIT, M.D.,
FREDERICK MURTAGH, M.D., AND MARC S. LAPAYOWKER, M . D .
Departments of Neurological Surgery and Radiology, St. Christopher's Hospital for Children, Temple University Health Sciences Center, Philadelphia, Pennsylvania ~" A technique employing a Doppler ultrasound flowmeter in determining cerebrospinal fluid shunt patency is described. The technique has proven to be a valuable aid in the evaluation of the patient in whom shunt function is in question. KEY WORDS 9 hydrocephalus 9 cerebrospinal fluid shunts ultrasound 9 Doppler technique
ins is a preliminary report on the utilization of Doppler flow detection to determine cerebrospinal fluid (CSF) shunt patency. The technique has been particularly useful in the management of patients whose clinical picture suggests shunt malfunction despite an apparently patent shunt as determined by manipulation of the flushing device of the system. Doppler flow detection depends on the changes in the frequency of sound waves reflected from moving acoustical interfaces. In the Doppler device the ultrasound waves are produced by electrical stimulation of a piezoelectric crystal; reflected waves are then detected by a second piezoelectric crystal. Waves that have been reflected from stationary acoustical interfaces are not changed in frequency and are electronically eliminated by the unit, while those that are reflected from moving interfaces have a frequency alteration and can be presented in the audible range.
T
728
9
Methods and Clinical Material
Method We have used a Parks Model 806 directional Doppler flowmeter* with the adjustable frequency output set at 9.5 MHz. The remote transducer from this unit is taped over the portion of the shunt to be tested. A liquid coupler is employed between the transducer and the skin to eliminate an air gap. With depression of the flushing device the examiner is then able to confirm shunt patency by hearing the flow over that portion of the tube. It is important that the transducer be independently secured so it does not move during the manipulation of the flushing device; without the elimination of such inadvertent movements, artifacts may lead to false *Parks Model 806 directional Doppler flowmeter made by Parks Electronic Laboratories, 12770 S.W. First Street, Beaverton, Oregon 97005. J. Neurosurg. / Volume 42 / June, 1975
Determination
of shunt patency by Doppler technique
positive results. We have also found that by varying the position of the transducer it is possible to minimize the interference emanating from the carotid artery or the abdominal aorta. Since our patients are in the pediatric age group, the problem of patient irritability and fussiness remains at times a significant test of the examiner's resolve. The characteristic response detected over the distal segment of the shunt tubing has two distinct components. We believe that the first of these represents the distal flow of CSF that occurs with depression of the flushing device, while the second sound is a lesser signal related to a slight reflux of CSF within the tubing. Tests on the proximal (ventricular) portion of the shunt demonstrate only a single response; this occurs with the release of the flushing device and we believe represents retrograde flow of CSF within the ventricular catheter. Case Material We have now examined 60 children with the Doppler technique. In 48 o f these who were clinically well, Doppler testing confirmed shunt patency in 44; each of the four remaining children in whom we were unable to confirm shunt function have since been followed for a sufficiently long period of time for us to speculate that they were shunt independent. The remaining 12 presented the problem we originally described, namely, a clinical picture suggesting shunt malfunction despite an apparently functional shunt as determined by manipulation of the flushing device. The Doppler technique has played a significant role in the management of this group of 12 children. Results Patients with No CSF Flow Through Shunt In seven of the 12 patients, testing demonstrated no CSF flow through the tubing. The following case history is representative of this group. Case Report. Three days prior to admission, this 41/E-year-old boy with communicating hydrocephalus associated with a myelomeningocele developed progressive lethargy, irritability, and vomiting. The child had had multiple shunt revisions since birth, and had been doing well with a ventriculoperitoneal (VP) shunt employing a Mischler-type flushing device. On examinaJ. Neurosurg. / Volume 42 / June, 1975
tion, the child was somnolent and irritable. Blood pressure was 120/60 mm Hg, heart rate 80 beats/min, temperature was 98.6~ The disc margins were distinct, although no central retinal vein pulsations could be noted. There were no focal neurological deficits, aside from motor impairment of the lower extremities present since birth. The flushing device of the VP shunt depressed and resumed its normal contour easily, suggesting proper functioning of the shunt. Intraventricular pressure was measured at 340 mm H20 by percutaneously tapping an Ommaya reservoir attached to a catheter in the right lateral ventricle; the apparatus had been previously installed as part of the treatment of an episode of ventriculitis. Doppler testing with the transducer placed over various portions of the distal shunt tubing revealed no evidence of flow during manipulation of the flushing device. When the scalp flap overlying the flushing device was opened in the operating room, no CSF was found flowing distally from that device. Testing of the peritoneal and ventricular catheters demonstrated them to be patent. A new flushing device was inserted. The patient's postoperative course was uneventful, and marked by resolution of his irritability and somnolence. Doppler testing of the shunt prior to discharge revealed evidence of flow in response to manipulation of the flushing device. We believe that incompetence of the internal valve of the flushing device resulted in reflux flow into the ventricle rather than distal flow through the peritoneal catheter. Other Shunt Revisions. Because we do not routinely perform either lumbar punctures or ventricular taps in patients with closed fontanels suspected of having a malfunctioning shunt, we were unable to document ventricular pressures in the remaining patients in this group who underwent shunt revision. However, at surgery each had a malfunctioning shunt, the causes for which included separation of the distal catheter from the flushing device, occlusion of the distal catheter with malfunctioning of the valve system of the flushing device, and blockage of the ventricular catheter. Patients with Functioning Shunt
In four of the remaining five patients Doppler technique demonstrated a functioning shunt; they were therefore observed 729
M. A. Flitter, et al. for an additional period of time. The subsequent development in these children of upper respiratory tract infections or gastroenteritis strengthened our long-held suspicion that in a hydrocephalic child the prodrome of a viral infection may at the outset simulate a shunt malfunction. The worsening clinical condition of the fifth child forced us to revise the shunt. At surgery the shunt seemed to be working; nevertheless, after the insertion of a new shunt system the child made an uneventful recovery. We concluded from this that the shunt had been working but was inadequate on a quantitative basis. Discussion
Alternate methods for confirming shunt function lack the simplicity of Doppler testing and frequently involve violation of subarachnoid space. The lumbar infusion test as described by Brisman, et al., 1 involves the analysis of the manometric response to the infusion of Ringer's lactate solution into the subarachnoid space. Intraventricular injection of radioactive iodinated serum albumin as suggested by Kagen, et al.? or injection of pertechnetate as reported by Rowan and Robertson, 4 both require ventricular taps and scanning over prolonged periods of time. In addition to those three methods, Go, et al., ~
730
described a technique that employed multiple thermistors and the analysis of the heat sink over the distal shunt tubing. We have found Doppler ultrasound evaluation of CSF shunt function to be a simple and safe procedure which may be repeated at frequent intervals. References
1. Brismhn R, Schneider S, Carter S: Lumbar CSF infusion test and shunt patency. Trans Am Neurol Assoc 96:212-213, 1971 2. Go KG, Veen van der PH, Berg van den JW: Detection of CSF flow in ventriculo-atrial shunts by cold transfer. Dev Med Child Neurol (Suppl) 22:69-72, 1970 3. Kagen H, Tsuchiya G, Patterson V, et al: Test for patency of ventriculovascular shunt for hydrocephalus with radioactive iodinated serum albumin. J Neurosurg 20:1025-1028, 1963 4. Rowan JO, Robertson JS: Evaluation of surgical ventricular shunts using sodium pertechnetate (Na99TCM04). Br J Rad 43:831, 1970
Address reprint requests to: Marc A. Flitter, M.D., Department of Neurological Surgery, St. Christopher's Hospital for Children, Temple University Health Sciences Center, Philadelphia, Pennsylvania.
J. Neurosurg. / Volume 42 / June, 1975
MARC A. FLITTER, M.D., WILLIAM A. BUCHHEIT, M.D.,
FREDERICK MURTAGH, M.D., AND MARC S. LAPAYOWKER, M . D .
Departments of Neurological Surgery and Radiology, St. Christopher's Hospital for Children, Temple University Health Sciences Center, Philadelphia, Pennsylvania ~" A technique employing a Doppler ultrasound flowmeter in determining cerebrospinal fluid shunt patency is described. The technique has proven to be a valuable aid in the evaluation of the patient in whom shunt function is in question. KEY WORDS 9 hydrocephalus 9 cerebrospinal fluid shunts ultrasound 9 Doppler technique
ins is a preliminary report on the utilization of Doppler flow detection to determine cerebrospinal fluid (CSF) shunt patency. The technique has been particularly useful in the management of patients whose clinical picture suggests shunt malfunction despite an apparently patent shunt as determined by manipulation of the flushing device of the system. Doppler flow detection depends on the changes in the frequency of sound waves reflected from moving acoustical interfaces. In the Doppler device the ultrasound waves are produced by electrical stimulation of a piezoelectric crystal; reflected waves are then detected by a second piezoelectric crystal. Waves that have been reflected from stationary acoustical interfaces are not changed in frequency and are electronically eliminated by the unit, while those that are reflected from moving interfaces have a frequency alteration and can be presented in the audible range.
T
728
9
Methods and Clinical Material
Method We have used a Parks Model 806 directional Doppler flowmeter* with the adjustable frequency output set at 9.5 MHz. The remote transducer from this unit is taped over the portion of the shunt to be tested. A liquid coupler is employed between the transducer and the skin to eliminate an air gap. With depression of the flushing device the examiner is then able to confirm shunt patency by hearing the flow over that portion of the tube. It is important that the transducer be independently secured so it does not move during the manipulation of the flushing device; without the elimination of such inadvertent movements, artifacts may lead to false *Parks Model 806 directional Doppler flowmeter made by Parks Electronic Laboratories, 12770 S.W. First Street, Beaverton, Oregon 97005. J. Neurosurg. / Volume 42 / June, 1975
Determination
of shunt patency by Doppler technique
positive results. We have also found that by varying the position of the transducer it is possible to minimize the interference emanating from the carotid artery or the abdominal aorta. Since our patients are in the pediatric age group, the problem of patient irritability and fussiness remains at times a significant test of the examiner's resolve. The characteristic response detected over the distal segment of the shunt tubing has two distinct components. We believe that the first of these represents the distal flow of CSF that occurs with depression of the flushing device, while the second sound is a lesser signal related to a slight reflux of CSF within the tubing. Tests on the proximal (ventricular) portion of the shunt demonstrate only a single response; this occurs with the release of the flushing device and we believe represents retrograde flow of CSF within the ventricular catheter. Case Material We have now examined 60 children with the Doppler technique. In 48 o f these who were clinically well, Doppler testing confirmed shunt patency in 44; each of the four remaining children in whom we were unable to confirm shunt function have since been followed for a sufficiently long period of time for us to speculate that they were shunt independent. The remaining 12 presented the problem we originally described, namely, a clinical picture suggesting shunt malfunction despite an apparently functional shunt as determined by manipulation of the flushing device. The Doppler technique has played a significant role in the management of this group of 12 children. Results Patients with No CSF Flow Through Shunt In seven of the 12 patients, testing demonstrated no CSF flow through the tubing. The following case history is representative of this group. Case Report. Three days prior to admission, this 41/E-year-old boy with communicating hydrocephalus associated with a myelomeningocele developed progressive lethargy, irritability, and vomiting. The child had had multiple shunt revisions since birth, and had been doing well with a ventriculoperitoneal (VP) shunt employing a Mischler-type flushing device. On examinaJ. Neurosurg. / Volume 42 / June, 1975
tion, the child was somnolent and irritable. Blood pressure was 120/60 mm Hg, heart rate 80 beats/min, temperature was 98.6~ The disc margins were distinct, although no central retinal vein pulsations could be noted. There were no focal neurological deficits, aside from motor impairment of the lower extremities present since birth. The flushing device of the VP shunt depressed and resumed its normal contour easily, suggesting proper functioning of the shunt. Intraventricular pressure was measured at 340 mm H20 by percutaneously tapping an Ommaya reservoir attached to a catheter in the right lateral ventricle; the apparatus had been previously installed as part of the treatment of an episode of ventriculitis. Doppler testing with the transducer placed over various portions of the distal shunt tubing revealed no evidence of flow during manipulation of the flushing device. When the scalp flap overlying the flushing device was opened in the operating room, no CSF was found flowing distally from that device. Testing of the peritoneal and ventricular catheters demonstrated them to be patent. A new flushing device was inserted. The patient's postoperative course was uneventful, and marked by resolution of his irritability and somnolence. Doppler testing of the shunt prior to discharge revealed evidence of flow in response to manipulation of the flushing device. We believe that incompetence of the internal valve of the flushing device resulted in reflux flow into the ventricle rather than distal flow through the peritoneal catheter. Other Shunt Revisions. Because we do not routinely perform either lumbar punctures or ventricular taps in patients with closed fontanels suspected of having a malfunctioning shunt, we were unable to document ventricular pressures in the remaining patients in this group who underwent shunt revision. However, at surgery each had a malfunctioning shunt, the causes for which included separation of the distal catheter from the flushing device, occlusion of the distal catheter with malfunctioning of the valve system of the flushing device, and blockage of the ventricular catheter. Patients with Functioning Shunt
In four of the remaining five patients Doppler technique demonstrated a functioning shunt; they were therefore observed 729
M. A. Flitter, et al. for an additional period of time. The subsequent development in these children of upper respiratory tract infections or gastroenteritis strengthened our long-held suspicion that in a hydrocephalic child the prodrome of a viral infection may at the outset simulate a shunt malfunction. The worsening clinical condition of the fifth child forced us to revise the shunt. At surgery the shunt seemed to be working; nevertheless, after the insertion of a new shunt system the child made an uneventful recovery. We concluded from this that the shunt had been working but was inadequate on a quantitative basis. Discussion
Alternate methods for confirming shunt function lack the simplicity of Doppler testing and frequently involve violation of subarachnoid space. The lumbar infusion test as described by Brisman, et al., 1 involves the analysis of the manometric response to the infusion of Ringer's lactate solution into the subarachnoid space. Intraventricular injection of radioactive iodinated serum albumin as suggested by Kagen, et al.? or injection of pertechnetate as reported by Rowan and Robertson, 4 both require ventricular taps and scanning over prolonged periods of time. In addition to those three methods, Go, et al., ~
730
described a technique that employed multiple thermistors and the analysis of the heat sink over the distal shunt tubing. We have found Doppler ultrasound evaluation of CSF shunt function to be a simple and safe procedure which may be repeated at frequent intervals. References
1. Brismhn R, Schneider S, Carter S: Lumbar CSF infusion test and shunt patency. Trans Am Neurol Assoc 96:212-213, 1971 2. Go KG, Veen van der PH, Berg van den JW: Detection of CSF flow in ventriculo-atrial shunts by cold transfer. Dev Med Child Neurol (Suppl) 22:69-72, 1970 3. Kagen H, Tsuchiya G, Patterson V, et al: Test for patency of ventriculovascular shunt for hydrocephalus with radioactive iodinated serum albumin. J Neurosurg 20:1025-1028, 1963 4. Rowan JO, Robertson JS: Evaluation of surgical ventricular shunts using sodium pertechnetate (Na99TCM04). Br J Rad 43:831, 1970
Address reprint requests to: Marc A. Flitter, M.D., Department of Neurological Surgery, St. Christopher's Hospital for Children, Temple University Health Sciences Center, Philadelphia, Pennsylvania.
J. Neurosurg. / Volume 42 / June, 1975
