CLINICAL STUDIES EVALUATING THE EFFECT OF DECOMPRESSION SURGERY ON CEREBROSPINAL FLUID FLOW AND INTRACRANIAL COMPLIANCE IN PATIENTS WITH CHIARI MALFORMATION WITH MAGNETIC RESONANCE IMAGING FLOW STUDIES Anusha Sivaramakrishnan, OBJECTIVE: To quantify the effect of decompression surgery on craniocervical junc- M.S. tion hydrodynamics and on global intracranial compliance (ICC) in patients with Department of Radiology, Chiari I malformation by use of magnetic resonance measurements of cerebrospinal University of Illinois at Chicago, Chicago, Illinois fluid and blood flow. Studying the effect of decompression surgery may improve our understanding of the pathophysiological characteristics of Chiari I malformation and Noam Alperin, Ph.D. aid in identifying patients who will benefit from the procedure. Department of Radiology, METHODS: Twelve patients were studied with a 1.5-T magnetic resonance imaging University of Illinois at Chicago, scanner before and after decompression surgery. Cine phase contrast magnetic reso- Chicago, Illinois nance images were used to quantify maximum cord displacement, maximum systolic Sushma Surapaneni, B.S. cerebrospinal fluid velocity and volumetric flow rate, and overall ICC. ICC was derived Department of Radiology, by use of a previously reported method that measures small changes in intracranial University of Illinois at Chicago, volume and pressure that occur naturally with each cardiac cycle. Chicago, Illinois RESULTS: After surgery, changes were documented both in the local hydrodynamic parameters and in ICC. However, only the change in ICC, an average increase of more Terry Lichtor, M.D., Ph.D. than 60%, was statistically significant. Increased ICC, which was associated with Department of Neurosurgery, Rush-Presbyterian St. Luke’s improved outcome, was measured in 10 of the 12 patients, no significant change was Medical Center, documented in 1 patient, and decreased ICC was measured in 1 patient whose Cook County Hospital, symptoms persisted after surgery. Chicago, Illinois CONCLUSION: An increase in the overall compliance of the intracranial compart- Reprint requests: ment is the most significant and consistent change measured after decompression Noam Alperin, Ph.D., surgery. Changes in cord displacement, cerebrospinal fluid velocities, and flow in the Physiological Imaging and Modeling Laboratory, Department craniospinal junction were less consistent and less affected by the operation. Thus, ICC of Radiology (M/C 711), University may play an important role in the outcome of decompression surgery related to of Illinois at Chicago, improving symptoms and restoring normal neurological hydrodynamics in patients 830 South Wood Street, Chicago, IL 60612. with Chiari I malformations. Email: firstname.lastname@example.org KEY WORDS: Cerebrospinal fluid flow, Chiari malformation, Cine phase contrast magnetic resonance imaging, Decompression surgery, Intracranial compliance Received, February 27, 2004. Accepted, August 19, 2004. Neurosurgery 55:1344-1351, 2004 DOI: 10.1227/01.NEU.0000143612.60114.2D www.neurosurgery-online.com C hiari I malformation is characterized by displacement of or syringomyelia, is more common. Typical symptoms in pa- the cerebellar tonsils more than 5 mm caudally through tients with Chiari I malformation include headache, neck pain, the foramen magnum (8, 15). The level of hindbrain her- and sensory and motor deficits. However, as no direct correlation niation is best revealed by midline sagittal T1-weighted magnetic has been observed between symptoms and the anatomic severity resonance imaging (MRI), which currently is used for diagnosis of herniation, the pathophysiological characteristics of the dis- of the disorder (13). Chiari I malformation is not commonly ease cannot be explained by the abnormal anatomy of the cra- associated with other cerebral anatomic abnormalities, although niospinal junction alone. association with hydrocephalus has been reported (14). Associa- Several investigators attempted to better understand the tion with spinal canal abnormalities, such as progressive scoliosis pathophysiological characteristics of Chiari I malformation by 1344 | VOLUME 55 | NUMBER 6 | DECEMBER 2004 www.neurosurgery-online.com CHANGES IN INTRACRANIAL COMPLIANCE WITH DECOMPRESSION SURGERY measuring cerebrospinal fluid (CSF) flow velocities at differ- of the CSF spaces and the posture of the neck and global ent locations around the craniospinal junction with cine phase factors such as cerebral hemodynamics and the biomechanical contrast MRI (7, 12, 18, 20, 22, 24). A quantitative study per- state of the craniospinal system (2, 5, 11, 16, 23). Therefore, formed by Shibuya et al. (24) in 31 patients with Chiari mal- there is a clear need for further study of the functional effect of formation demonstrated that the amplitude of CSF velocities decompression surgery to analyze parameters that may be less at the C3 level posterior to the cord decreases with increased variable. hindbrain herniation. Pujol et al. (22) reported higher tonsillar Our group recently developed a system-based analysis of pulsations with delayed upward CSF flow in patients with MRI measurements of CSF and blood flow to characterize the Chiari malformation compared with normal subjects. In a craniospinal hydrodynamics as well as overall intracranial similar study, Hofmann et al. (18) demonstrated an increase in compliance (ICC). Decompression-related changes in the up- maximum systolic and diastolic cord displacement rates and per cervical spine hydrodynamics and in the overall ICC are an impairment of upward flow in the anterior and posterior measured and evaluated for their significance. The ICC is CSF spaces of the spinal canal in patients with Chiari malfor- derived from volumetric flow rates (VFRs) of blood and CSF mations. Altered CSF flow velocities and cord motion dynam- flow to and from the intracranial vault. The ICC measurement ics are associated with Chiari I malformation; however, the is based on the phasic changes in intracranial volume and clinical relevance of these findings and their contribution to pressure that occur naturally during the cardiac cycle. The the understanding of the pathophysiological characteristics of decompression surgery-related changes in ICC, maximum the disorder has been limited. value of mean CSF velocity at C2, maximum CSF VFR, CSF Although the disease process is not well understood, de- volume that oscillates between the cranium and spinal canal, compression surgery is now commonly offered as a treatment and maximal cord displacement were compared and evalu- of choice for patients with Chiari malformation with or with- ated for their statistical significance. out syringomyelia. Surgical options include decompression with or without opening of the dura mater, opening of the PATIENTS AND METHODS dura with or without closing or patching, lysis of adhesions and exploration of the 4th ventricle with or without obex Patients plugging or stenting of the ventricle, resection of the tonsils, and various shunting procedures for the syrinx itself (21). The Twelve patients were studied before and after decompres- outcome of decompression surgery usually is evaluated by sion surgery (eight women and four men; age range, 30–58 yr; comparing symptoms before and after surgery. Good outcome mean age, 42 8 yr) by use of a 1.5-T MRI Signa scanner is usually reported after surgery (6), although failed decom- (General Electric Medical systems, Milwaukee, WI). The study pression with either persistence or reoccurrence of symptoms protocol was approved by the institutional review board, and several months after decompression also has been reported consent was obtained from all patients. Of these 12 patients, 4 (10, 17, 19). had Chiari I malformation alone, 5 had Chiari I malformation Badie et al. (9) analyzed the anatomic posterior fossa ratio as and syringomyelia, and 3 had Chiari I malformation and a means to predict response to suboccipital decompressive hydrocephalus. One patient with syringomyelia had a history surgery. They reported a smaller posterior fossa ratio in pa- of craniofacial surgery for Crouzon’s disease. Symptoms in tients with Chiari malformation compared with control sub- these patients included headache, neck pain, and sensory and jects and further demonstrated that a smaller posterior fossa motor difficulties (such as vertigo, ataxia, and dysmetria). The ratio is associated with better surgical outcome. Bhadelia et al. tonsillar herniation ranged from 5 to 17 mm (mean, 9.3 mm; (12) investigated the functional effect of decompression sur- standard deviation, 3.8 mm). All patients underwent suboc- gery by measuring systolic and diastolic CSF flow velocities at cipital craniectomy, C1 laminectomy, and duraplasty. The four different regions in the craniospinal junction and the three patients with hydrocephalous did not undergo any ad- upper cervical subarachnoid space with MRI . They reported ditional procedures such as placement of a shunt, with the a statistically significant increase in maximum CSF velocities exception of one patient who had a temporary external ven- after decompression surgery only in the anterior subarachnoid tricular drainage placed during the operation, which was re- space below the foramen magnum. Armonda et al. (7), how- moved on postoperative Day 13. Eleven of the patients re- ever, measured significant change in CSF velocity only dorsal ported improvement in symptoms, and one patient (with to the spinal cord at the level of C2. This inconsistency is not syringomyelia) reported persistence of symptoms and weak- surprising, as CSF flow velocity changes considerably from ness and numbness in one hand. one region to another within the complex anatomy of the craniospinal junction. MRI Parameters CSF velocity has been demonstrated to vary considerably Standard anatomic sagittal T1-weighted MRI scans were among individuals, even when measured in the same location used to estimate herniation levels in all patients before sur- (11, 25). This known intersubject variability in CSF velocity gery. Hydrodynamic parameters and ICC were obtained from may be attributable to the many factors that modulate CSF measurements of CSF and blood flows to and from the cra- flow. These include local factors such as the variable geometry nium with low- and a high-velocity encoded cine phase con- NEUROSURGERY VOLUME 55 | NUMBER 6 | DECEMBER 2004 | 1345 SIVARAMAKRISHNAN ET AL. trast scans, respectively. Blood flow was imaged by velocity encoding ranging from 60 to 90 cm/s, and the slower CSF flow was imaged by velocity encoding ranging from 5 to 9 cm/s. The CSF flow was measured at mid C2 level, where the luminal cross sectional area is relatively unchanged, to obtain reliable velocity and VFR measurements. Other imaging pa- rameters were as follows: slice thickness, 5 to 6 mm; field of view, 14 to 16 cm; repetition time, 17 to 22 milliseconds; echo time, 6.5 to 9 milliseconds; and flip angle of 20 and 25 degrees for the CSF and blood flow scans, respectively. Derivation of Hydrodynamic Parameters CSF flow between the cranium and spinal canal was mea- FIGURE 1. A compartmental model proposed by Alperin et al. (1) used for the derivation of the intracranial volume change. The model shows sured with the low-velocity encoding images. CSF velocities arterial inflow, venous outflow to the cranium, and oscillating CSF flow inside the cross sectional area of the CSF space were averaged between the cranium and spinal canal. During systole, arterial blood to obtain the mean CSF velocity. The VFR then was obtained inflow is greater than venous and CSF outflow, causing the small change by multiplying the mean velocity by the CSF space cross in intracranial volume. sectional area. The cord displacement rates during the cardiac cycle were derived by multiplying the mean cord velocity by the Navier-Stokes equation (3). An ICC index (CI) then was its cross sectional area. Cord displacement was then obtained calculated from the ratio of these small changes in intracranial by integration with respect to time during the cardiac cycle. volume and pressure that occur naturally with each cardiac For increased measurement accuracy and reproducibility, lu- cycle (3, 23). men boundaries were delineated with a recently developed automated method for segmentation of lumens conducting pulsatile flow, the pulsatility-based segmentation technique Data Analysis (1). The parameters analyzed were maximum cord displace- The effect of decompression surgery was quantified by ment, maximum value of mean CSF velocity during the sys- comparing changes in the analyzed parameters before and tolic phase, and maximum value of CSF VFR during the after surgery. Student’s single-tailed paired t test was per- systolic phase. The amount of CSF volume that flows from and formed on the pre- and postdecompression parameters for all to the intracranial vault (i.e., oscillatory CSF volume) was 12 patients and separately for the 9 patients without hydro- obtained by integrating the absolute values of the CSF flow cephalus by use of SYSTAT software, Version 8 (SYSTAT waveform during the cardiac cycle and dividing the sum by Software, Inc., Richmond, CA). A P value of 0.05 was con- two. Intersubject average and standard deviation before and sidered a statistically significant difference. after surgery then were calculated. Derivation of ICC RESULTS The neurophysiological basis for the derivation of the intra- Sagittal T1-weighted anatomic images from patients with cranial volume change during the cardiac cycle was explained and without hydrocephalous, before and after decompression according to the simplified compartmental model of the cra- surgery are shown in Figure 2. An example of an MRI scan niospinal system (Fig. 1). The intracranial volume change was used for quantitation of the blood flow to and from the brain derived from the instantaneous difference among volumetric is shown in Figure 3. A scout magnetic resonance angiogram arterial inflow, venous outflow, and oscillating CSF flow be- scan also is shown to indicate the location of the blood flow tween the cranium and spinal canal. During systole, arterial velocities measurement. In the velocity encoded image, black inflow is greater than venous and CSF outflows, resulting in a pixels indicate flow in cranial direction (arterial inflow), and small temporary increase in volume that in turn causes an white pixels indicate flow in the caudal direction (venous increase in pressure. Total arterial inflow to the cranium was outflow). Graphs of total arterial (filled) and venous (open) calculated by summation of the VFR through each of the four VFR waveforms before and after decompression surgery for vessels carrying blood to the brain (right and left internal the same patient are shown in Figure 4. Arterial blood flow is carotid arteries and the right and left vertebral arteries). Ve- relatively unaffected by the surgery. An example of an MRI nous outflow was obtained by summation of the flow through scan used for quantitation of CSF flow is shown in Figure 5. A the internal jugular veins and epidural, vertebral, and deep sagittal T1-weighted MRI scan with the slice location for the cervical veins when present. Pressure change during the car- CSF flow measurements also is shown. Graphs of the CSF VFR diac cycle was derived from the change in the CSF pressure waveforms before and after surgery are shown in Figure 6. In gradient. The CSF pressure gradient waveform was calculated this patient, CSF VFR during the systolic phase is lower after from the velocity-encoded MRI images of the CSF flow with surgery compared with VFR measured before surgery. The 1346 | VOLUME 55 | NUMBER 6 | DECEMBER 2004 www.neurosurgery-online.com CHANGES IN INTRACRANIAL COMPLIANCE WITH DECOMPRESSION SURGERY FIGURE 4. MRI-derived measurements of total arterial inflow (closed circles) and total venous outflow (open circles) for a patient before (A) and after (B) decompression surgery. The flow dynamic and the total arte- rial VFR before and after surgery were not affected by the operation. FIGURE 2. Midsagittal T1-weighted MRI scans used to diagnose Chiari I malformation and assess the level of herniation. A and B, a patient with syrinx and without hydrocephalus before (A) and after (B) decompression surgery. C and D, a patient with hydrocephalus before (C) and after (D) decompression surgery. FIGURE 5. A, phase contrast MRI scan of systolic CSF flow through the spinal canal used for the calculation of the CSF VFR. B, anatomic midsag- ittal T1-weighted MRI scan showing the location of the low-velocity encoded cine phase contrast MRI scan used for CSF flow measurement. FIGURE 3. A, phase contrast MRI scan of blood vessels to and from the FIGURE 6. The VFR waveforms of CSF before (A) and after (B) decom- cranium. Black, arterial flow toward the cranium; white, venous flow pression surgery. A reduction in the amplitude of the CSF VFR waveform from the cranium. B, blood vessel MRI scout image showing the location is observed after surgery. The lower heart rate during the postoperative of the axial slice for blood flow measurements. MRI study (longer cardiac cycle period) may have contributed to this reduction. lower VFR could have resulted from the longer cardiac cycle (lower heart rate) during the postoperative study. Average intersubject values of maximum cord displace- 0.05). The average CI increased 64%, from 6.9 before surgery to ment, maximum CSF systolic velocity, maximum CSF systolic 11.3 after surgery. The effect of surgery on ICC also was VFR, CSF oscillatory volume, and CI, before and after surgery, evaluated separately in the nine patients who did not have are summarized in Table 1. On average, cord displacement hydrocephalus to eliminate its possible contribution to the decreased by 21% after surgery, CSF systolic velocity de- overall ICC. The distribution of the intracranial CI for the nine creased by only 2%, maximum CSF VFR decreased by 15%, patients with Chiari malformation without hydrocephalus is and the oscillatory CSF volume decreased by 13%. None of the shown in Figure 7. The preoperative average CI for these 9 changes in these parameters reached statistical significance. In patients was slightly higher (7.7) compared with the average contrast, the change in CI was statistically significant (P for all 12 patients, possibly owing to the effect of the hydro- NEUROSURGERY VOLUME 55 | NUMBER 6 | DECEMBER 2004 | 1347 SIVARAMAKRISHNAN ET AL. TABLE 1. Summary of magnetic resonance imaging-derived hydrodynamic parameters before and after decompression surgerya Presurgery Postsurgery P value (mean SD) (mean SD) Max. cord 0.32 0.18 0.25 0.12 0.14 displacement (mm) Max. mean CSF 1.60 0.45 1.56 0.64 0.39 velocity (cm/s) FIGURE 8. Net transcranial A V blood flow (closed circles) and the Max. CSF VFR 180.5 42.3 153.5 60.7 0.11 CSF flow waveforms to the craniospinal system (open circles), before (ml/min) decompression (A) and after decompression (B). The CSF waveform fol- Oscillatory CSF 0.53 0.2 0.46 0.21 0.12 lows the A V waveform more closely before decompression. Volume (ml) ple of the net transcranial blood flow (arterial inflow minus Compliance index 6.9 4.6 11.3 5.8 0.01b venous outflow [A V]) as well as the CSF VFR waveforms (all patients) before and after surgery. Before surgery, the CSF waveform Compliance index c 5.9 3.1 10.3 4.9 0.02b “follows” the A V waveform more closely than it does after surgery. Because the net transcranial blood flow can be re- a SD, standard deviation; max., maximum; CSF, cerebrospinal fluid; VFR, garded as the driving force of the CSF flow, the less compliant volumetric flow rate. b Statistical significance (P 0.05). intracranial compartment before surgery causes the CSF c Excluding patient with Crouzon’s disease. waveform to follow the A V waveform more closely (5). CONCLUSION This study expands earlier work performed by other groups, who used dynamic MRI measurements to quantify the effect of decompression surgery on local craniospinal junction hydrodynamics with measurements of cord displacement and CSF flow velocity. In the present study, changes in local hy- drodynamics also were measured and then compared with the change in ICC. Previous studies demonstrated that patients with Chiari malformation had higher tonsillar pulsations (22) and rates of cord displacement (18) compared with healthy subjects. Therefore, the finding of larger cord displacement before surgery in this study is in agreement with the results of earlier reports. It is possible that the difference in this param- eter did not reach statistical significance in the current study FIGURE 7. Graph representing the change in CI after the decompression because of the large intersubject variability in tonsillar herni- surgery among patients with Chiari malformation without hydrocephalus. ation (5–17 mm), which may have contributed to the variabil- Possible reasons for the decrease in CI demonstrated in one patient ( ) ity in cord displacement. and considerably larger values in another patient ( ) are described above In the present study, mean CSF velocity, averaged for the in the Discussion. entire cross sectional area, was used to represent CSF veloci- ties at the upper cervical spine. The average maximum CSF velocity was relatively unaffected by surgery. This finding cephalous. The postoperative average CI in these 9 patients does not corroborate those in previous reports (7, 12), which increased to 11.9. After surgery, an increase in ICC was dem- had documented statistically significant increases in CSF ve- onstrated in 10 of the 12 patients, was relatively unchanged in locity at selected locations after decompression surgery. one patient, and was significantly decreased in one patient. Bhadelia et al. (12) observed significant increase in velocity The decreased ICC was demonstrated in a patient whose only in the anterior subarachnoid space below the foramen symptoms persisted after surgery. magnum, and Armonda et al. (7) reported increased velocity The increase in ICC after decompression is demonstrated by only in the dorsal region at C2. These studies demonstrate the the change in the relationship between the CSF and the net variability in velocity measurements and the strong depen- transcranial blood flow waveforms. Figure 8 shows an exam- dence on the choice of the region of interest. Therefore, the 1348 | VOLUME 55 | NUMBER 6 | DECEMBER 2004 www.neurosurgery-online.com CHANGES IN INTRACRANIAL COMPLIANCE WITH DECOMPRESSION SURGERY relatively unchanged mean CSF velocity demonstrated in the Although a decrease in the maximum amplitude of the CSF current study can be attributed to the difference in the location velocity at C3 was reported to correlate with the severity of the of the measurement as well as in the inherent large variability tonsillar herniation (24), MRI measurements of CSF velocity in in the distribution of CSF velocities in the cervical spine region the craniospinal junction are not widely used to assess the (25). functional severity associated with Chiari malformation. The Unlike the local hydrodynamic parameters, the difference in lack of correlation between the degree of the herniation and ICC measured before and after surgery was statistically sig- severity of symptoms further limits the usefulness of local nificant, even with the relatively smaller number of patients hydrodynamics parameters such as CSF velocity alone to char- used in this study. There was a clear trend of increased ICC acterize the pathophysiological characteristics of Chiari I after surgery. Increased ICC was demonstrated in eight of the malformation. nine patients without hydrocephalus, and in two of the three This study quantifies for the first time the effect decompres- patients with hydrocephalus. The average CI measured before sion surgery has on overall ICC. It further suggests that the surgery in 11 patients (excluding the patient with Crouzon’s change in ICC may have a greater significance than previously reported changes in local hydrodynamic parameters. This po- disease) was 5.9. This value is considerably lower than the tentially establishes the CI derived from MRI measurements average CI (8.24 2.42) previously reported in young healthy as a more sensitive indicator of the mechanical state of the subjects (4). This finding supports the hypothesis by Hofmann system compared with CSF velocity alone. The finding of et al. (18) that associates the increase in cord movement with decreased CSF VFR after surgery can be explained in relation decreased ICC in patients with Chiari I malformation. to the increased ICC with decompression surgery. Because the craniospinal system is more compliant after surgery, it is able to accommodate the increased arterial inflow and blood vol- Relationship between Outcome and Change in ICC ume during systole with a lesser amount of CSF displaced The increased ICC after decompression surgery in 10 of the from the cranium to the spinal canal. 12 patients studied also was associated with improved clinical This study supports suggestions by other investigators that outcome. The abnormal decrease in the ICC after surgery ICC has a potentially important role in the pathophysiological occurred in a patient with approximately 10 mm of herniation characteristics of Chiari malformation and the effect of decom- and a syrinx extending from C2–C4. This patient presented pression surgery (10, 18). In a report of failed decompression with weakness in the right hand, which persisted after sur- surgery treatment, Bejjani et al. (10) discuss the need to deter- gery. An unusual thickening of the arachnoid membrane with mine the compliance of the system before and after surgery to adhesions was noted during surgery. It is possible that this better understand the reasons for failure, which could be abnormal thickening and the adhesions were further aggra- addressed by additional treatment such as lumbar puncture or vated by the surgery, and that this was the reason for the ventricular shunting. Further study in a larger number of decrease in ICC. Arachnoid scarring has been reported previ- patients with negative outcome would be needed to substan- ously by Bejjani et al. (10) as a potential cause for surgical tiate a correlation between decreased ICC and negative out- complications and failure. Thus, decreased ICC probably can come. The ability to quantify ICC, noninvasively by MRI, be associated with a poor surgical outcome in that patient. The could potentially help identify the most effective treatment among the different decompression procedures currently of- second patient in whom the change in ICC did not follow the fered. In addition, the MRI-based ICC measurement could be trend also had hydrocephalus. An insignificant decrease in used to identify patients who may not benefit from decom- ICC was measured after surgery, although most symptoms of pression surgery, thereby reducing failure rate and improving headaches reported by this patient have resolved. The one overall outcome. patient with abnormally high ICC values both before and after surgery (Fig. 7) had syringomyelia and had undergone previ- ous craniofacial surgery for the treatment of Crouzon’s dis- REFERENCES ease, which may explain the high CIs before and after surgery. The increase in CI after decompression surgery is visually 1. Alperin N, Lee SH: PUBS: Pulsatility based segmentation of lumens con- ducting nonsteady flow. Magn Reson Med 49:934–944, 2003. evident from the relationship between CSF and the transcra- 2. Alperin N, Stelzig C: Does CSF flow reflect the mechanical state of the nial net A V waveforms before and after surgery (Figure 8). craniospinal system? Presented at the 7th International Society of Magnetic The transcranial A V blood flow can be regarded as the Resonance in Medicine, Philadelphia, Pennsylvania, May 24–28, 1999. 3. Alperin N, Lee SH, Loth F, Raksin PB, Lichtor T: MR-Intracranial pressure input to the intracranial system and the CSF flow as the (ICP): A method to measure intracranial elastance and pressure output. For a given pulsatile input inflow, the output flow noninvasively by means of MR imaging—Baboon and human study. Radi- would be less pulsatile (smoother) for the system with a larger ology 217:877–885, 2000. CI. The A V waveform shown is followed more closely by 4. Alperin N, Lee SH, Sivaramakrishnan A, Lichtor T, Blend M, Hemmati M: Determining the false positive rate of a new MRI-based method for simul- the CSF waveform in the preoperative than the postoperative taneous measurement of total cerebral blood flow and ICP. Presented at the example, indicating that the intracranial compartment is more 89th Scientific Assembly and Annual Meeting of Radiological Society of compliant after surgery than before. North America, Chicago, Illinois, November 30–December 5, 2003. NEUROSURGERY VOLUME 55 | NUMBER 6 | DECEMBER 2004 | 1349 SIVARAMAKRISHNAN ET AL. 5. Alperin N, Vikingstad EM, Gomez-Anson B, Levin DN: Hemodynami- Acknowledgments cally independent analysis of cerebrospinal fluid and brain motion ob- served with dynamic phase contrast MRI. Magn Reson Med 35:741–754, We thank Ed and Gayle Labuda from the Charitable Fund of the Vanguard 1996. Charitable Endowment Program for financial support. 6. Alzate JC, Kothbauer KF, Jallo GI, Epstein FJ: Treatment of Chiari type I malformation in patients with and without Syringomyelia: A consecutive series of 66 cases. Neurosurg Focus 11:Article 3, 2001. COMMENTS 7. Armonda RA, Citrin CM, Foley KT, Ellenbogen RG: Quantitative cine-mode magnetic resonance imaging of Chiari I malformations: An analysis of cerebrospinal fluid dynamics. Neurosurgery 35:214–224, 1994. 8. Arnett B: Arnold-Chiari malformation. Arch Neurol 60:898–900, 2003. S ivaramakrishnan et al. have provided a valuable addition to the body of knowledge regarding the pathophysiology and management of the Chiari malformation. They studied 12 9. Badie B, Mendoza D, Batzdorf U: Posterior fossa volume and response to patients, both before and after surgery, regarding magnetic suboccipital decompression in patients with Chiari I malformation. Neuro- resonance imaging cine flow hydrodynamic characteristics at surgery 37:214–218, 1995. 10. Bejjani GK, Cockerham KP, Rothfus WE, Maroon JC, Maddock M: Treat- the cervicomedullary junction. They studied spinal cord dis- ment of failed adult Chiari malformation: Decompression with CSF drain- placement, volumetric flow rate, cerebrospinal fluid velocity, age observations in six patients. Acta Neurochir (Wien) 145:107–116, 2003. and intracranial compliance. Most notably, they observed an 11. Bhadelia RA, Bogdan AR, Wolpert SM: Analysis of the cerebrospinal fluid increase in intracranial compliance after decompression. This flow waveform using gated phase contrast MR velocity measurements. suggests a global and far-reaching effect of symptomatic AJNR Am J Neuroradiol 16:389–400, 1995. Chiari malformations, as well as providing insight into their 12. Bhadelia RA, Bogdan AR, Wolpert SM, Lev S, Appignani BA, Heilman CB: Cerebrospinal fluid flow waveforms: Analysis in patients with Chiari I pathophysiology. Gradually, we are beginning to “under- malformation by means of gated phase-contrast MR imaging velocity mea- stand” the Chiari malformation and its ramifications. Sivara- surements. Radiology 196:195–202, 1995. makrishnan et al. have most certainly contributed to this body 13. Cama A, Tortori-Donati P, Piatelli GL, Fondelli MP, Andreussi L: Chiari of knowledge with this article. complex in children: Neuroradiological diagnosis, neurosurgical treatment and proposal of a new classification (312 cases). Eur J Pediatr Surg 5[Suppl Edward C. Benzel 1]:35–38, 1995. Cleveland, Ohio 14. Caviness VS: The Chiari malformations of the posterior fossa and their relation to hydrocephalus. Dev Med Child Neurol 18:103–116, 1976. 15. Elster AD, Chen MY: Chiari I malformations: Clinical and radiologic reap- praisal. Radiology 183:347–353, 1992. T he authors have studied a group of 12 patients before and after decompression for the hindbrain herniation syn- drome (Chiari I malformation) by use of magnetic resonance 16. Enzmann DR, Pelc NJ: Normal flow patterns of intracranial and spinal imaging. Cine face contrast images were used to quantify cord cerebrospinal fluid defined with phase contrast cine MR-imaging. Radiol- ogy 178:467–474, 1991. displacement, cerebrospinal fluid velocity, and volumetric 17. Guyotat J, Bret P, Jouanneau E, Ricci AC, Lapras C: Syringomyelia associ- flow rate as well as the intracranial compliance. Their results ated with type I Chiari malformation: A 21 year retrospective study on 75 showed an increased overall intracranial compliance in 10 of cases treated by foramen magnum decompression with a special emphasis 12 patients. This information improves our understanding of on the value of tonsils resection. Acta Neurochir (Wien) 140:745–754, 1998. some of the changes that occur with tonsillar impaction and 18. Hofmann E, Warmuth-Metz M, Bendszus M, Solymosi L: Phase contrast MR intracranial compliance as well as cerebrospinal fluid flow imaging of the cervical CSF and spinal cord: Volumetric motion analysis in patients with Chiari I malformation. AJNR Am J Neuroradiol 21:151–158, dynamics. However, the decision to operate on problematic 2000. patients and gain information with preoperative assessment 19. Levy WJ, Mason L, Hahn JF: Chiari malformation presenting in adults: A requires further elucidation. surgical experience in 127 cases. Neurosurgery 12:377–390, 1983. 20. Menick BJ: Phase contrast magnetic resonance imaging of cerebrospinal Arnold H. Menezes fluid flow in the evaluation of patients with Chiari I malformation. Iowa City, Iowa Neurosurg Focus 1:Article 5, 2001. 21. Park JK, Gleason PL, Madsen JR, Goumnerova LC, Scott RM: Presentation and management of Chiari I malformation in children. Pediatr Neurosurg 26:190–196, 1992. T his is an interesting submission. The authors have used contemporary imaging technology to measure intracranial compliance and assess the effects of suboccipital craniectomy 22. Pujol J, Roig C, Capdevila A, Pou A, Marti-Vilalta JL, Kulisevsky J, Escartin and C1 laminectomy with duroplasty in the treatment of A, Zannoli G: Motion of the cerebellar tonsils in Chiari type I malformation symptomatic patients with a Chiari I malformation. studied by cine phase-contrast MRI. Neurology 45:1746–1753, 1995. 23. Raksin P, Alperin N, Sivaramakrishnan A, Surapaneni S, Lichtor T: Intracranial compliance was found to be substantially im- Noninvasive intracranial compliance and pressure from dynamic MR im- proved after decompressive surgery in 10 of 12 patients. This aging of blood and CSF flows: Review of principles, implementation, and work is a contribution to our knowledge base on this topic. We other noninvasive approaches. Neurosurg Focus 14:Article 4, 2003. now can objectively assess patients before and after decom- 24. Shibuya R, Yonenobu K, Koizuma T, Kato Y, Mitta M, Yoshikawa H: pression to document whether our surgical procedure has had Pulsatile cerebrospinal fluid flow measurement using phase-contrast mag- its intended effect (to improve intracranial compliance). I look netic resonance imaging in patients with cervical myelopathy. Spine 27: forward to the study of changes in compliance and outcome to 1087–1093, 2002. 25. Thomsen C, Stahlberg F, Stubgaard M, Nordell B: Fourier analysis of cere- determine whether improved compliance truly translates into brospinal fluid flow velocities: MR imaging study—The Scandinavian Flow better outcome. This type of assessment has broad potential Group. Radiology 177:659–665, 1990. application for patients with increased intracranial pressure 1350 | VOLUME 55 | NUMBER 6 | DECEMBER 2004 www.neurosurgery-online.com CHANGES IN INTRACRANIAL COMPLIANCE WITH DECOMPRESSION SURGERY and reduced intracranial compliance from any cause, particu- mations. This is a small group of patients, and it will be useful larly when attempting to discern whether a previously suc- to examine such studies in a larger group and in a repeated cessfully treated patient is again symptomatic from scarring, manner. A correlation with clinical outcome would be impor- shunt dysfunction, tumor recurrence, or other cause. tant to our understanding of the physiology of Chiari I mal- formations and associated syringomyelia. Alteration in sys- Mark N. Hadley tolic cerebrospinal fluid flow and velocity, cerebrospinal fluid Birmingham, Alabama oscillatory volume, and intracranial compliance may be useful parameters to assess patient outcomes, and although local T he authors have examined in detail a small number of patients with Chiari I malformation by use of preoperative and postoperative cine magnetic resonance imaging. Determi- hydrodynamic parameters were found to be less sensitive to decompressive surgeries, studies in additional patients may nation of cerebrospinal fluid velocities can be complex, and help clarify the subgroups in which such parameters are im- consistency of such measurements can be difficult to achieve portant. As a whole, this is an interesting paper that adds to our understanding and suggests new ways of using cine mag- unless a clear location for comparison is identified. netic resonance imaging to assess the pathophysiology of Calculation of intracranial compliance is crucial to a variety Chiari malformations. of problems in neurosurgery. The use of this technique by the authors demonstrates a significant increase in intracranial Karin M. Muraszko compliance after surgical decompression of Chiari I malfor- Ann Arbor, Michigan Country Dance (pastel and oil on canvas, 1921) by Picasso (courtesy of the Picasso Museum, Paris).
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