High-Resolution MRI for Evaluation of Ventriculostomy Tubes: Assessment of Positioning and Proximal Patency.

BACKGROUND AND PURPOSE: Imaging evaluation of ventriculostomy tubes, despite the frequency of malfunction, has remained inadequate due to the absence of a systematic way of assessing the catheter itself. In this retrospective review, we assessed the utility of high-resolution 3D MR imaging techniques, including CISS and volumetric interpolated breath-hold examination sequences, in the evaluation of ventriculostomy catheters. MATERIALS AND METHODS: We performed a retrospective review of 23 clinical MR imaging cases of shunted hydrocephalus spanning a 3-year period, all depicting ventriculostomy catheters. The MR imaging examinations included isotropic CISS and volumetric interpolated breath-hold examination sequences performed with and without contrast. These were independently evaluated by 2 neuroradiologists with respect to the catheter course, side hole position, relationship of the side holes to the ventricles, patency, and the presence or absence of intraluminal debris. RESULTS: The catheter tip was best seen on isotropic CISS sequences reformatted in an oblique plane, and side holes were visualized as CSF signal defects along the catheter wall in 10/23 (43%) cases. The relationship of the catheter side holes to the ventricles was seen in 47% of cases and was best visualized on the coronal CISS sequences. Catheter patency was confirmed in 12/23 (52%) cases, while the other 48% were notable for T2 hypointense filling defects compatible with luminal obstruction. Enhancement of some of these filling defects on imaging is suggestive of choroid plexus ingrowth rather than debris. CONCLUSIONS: High-resolution 3D MR imaging using isotropic CISS sequences allows systematic evaluation of catheter positioning, patency, and potential etiologic differentiation of filling defects when shunt dysfunction is suspected.

Does Phase-Contrast Imaging through the Cerebral Aqueduct Predict the Outcome of Lumbar CSF Drainage or Shunt Surgery in Patients with Suspected Adult Hydrocephalus?

BACKGROUND AND PURPOSE: Radiologic imaging plays a key role in diagnosing chronic adult hydrocephalus, but its role in predicting prognosis is still controversial. We sought to evaluate the effectiveness of cardiac-gated phase-contrast MR imaging through the cerebral aqueduct in predicting the clinical response to diagnostic lumbar puncture/lumbar drainage and shunt surgery in suspected adult hydrocephalus. MATERIALS AND METHODS: In this retrospective study, the phase-contrast MR imaging of 185 patients with suspected chronic adult hydrocephalus was evaluated using the CSF Flow software package. Decision-making for shunt placement was performed in this cohort on the basis of clinical assessment alone without the availability of quantitative phase-contrast MR imaging results. We recorded the response to lumbar puncture or lumbar drainage and shunt surgery using quantitative tests such as the Tinetti Test, the Timed Up and Go, and the Mini-Mental State Examination and qualitative measures of gait, urinary, and cognitive symptom improvement before and after lumbar puncture/lumbar drainage and shunt surgery. Quantitative analysis of phase-contrast MR imaging was compared with clinical outcome measures. RESULTS: Both CSF stroke volume and flow rate overlapped between lumbar puncture/lumbar drainage responders and nonresponders. There was also a significant overlap between shunt responders and nonresponders. Aqueductal stroke volume or flow rate alone was a poor predictor of lumbar puncture/lumbar drainage and shunt surgery response. Quantitative clinical measures after lumbar puncture/lumbar drainage were better predictors of shunt response. CONCLUSIONS: This study suggests that the results of phase-contrast MR imaging through the cerebral aqueduct alone should not be used to select patients for diagnostic or therapeutic CSF diversion.

Natural History of Endoscopic Third Ventriculostomy in Adults: Serial Evaluation with High-Resolution CISS.

BACKGROUND AND PURPOSE: Endoscopic third ventriculostomy is a well-accepted treatment choice for hydrocephalus and is used most frequently with a known impediment to CSF flow between the third ventricle and basal cisterns. However, there are scarce data on the imaging evolution of the defect in the floor of the third ventricle and how this affects patency rates and clinical outcomes. The purpose of this study was to assess whether, and how, the endoscopic third ventriculostomy defect changes in size with time. MATERIALS AND METHODS: All high-resolution endoscopic third ventriculostomy protocol MRIs performed between 2009 through 2014 were retrospectively identified. Two fellowship-trained neuroradiologists, blinded to clinical information, independently reviewed all retrospective cases. RESULTS: A total of 98 imaging studies were included from 34 patients. The average change in the area throughout the studied period was 0.02 mm2/day (7.5 mm2/year), with a higher increase in size noted in the first 3 postsurgical months, with a gradual decrease in the degree of defect-size change. Use of the NICO Myriad device was correlated with the area of the endoscopic third ventriculostomy defect on the last follow-up, demonstrating a larger final defect size in patients in whom the surgical technique included debridement of the endoscopic third ventriculostomy defect walls with the NICO Myriad device (28.21 versus 11.25 mm, P < .05). CONCLUSIONS: High-resolution MR imaging with sagittal CISS images is useful in the postoperative evaluation of endoscopic third ventriculostomies. Such findings may prove useful in determining the optimal duration of follow-up with MR imaging of patients who have undergone endoscopic third ventriculostomy.

Does the Presence or Absence of DESH Predict Outcomes in Adult Hydrocephalus?

BACKGROUND AND PURPOSE: The DESH (disproportionately enlarged subarachnoid-space hydrocephalus) pattern of "tight high-convexity and medial subarachnoid spaces, and enlarged Sylvian fissures with ventriculomegaly" is used to determine which patients undergo an operation for adult hydrocephalus at many centers. Our aim was to review adult hydrocephalus cases when DESH has not been a criterion for an operation to determine the prevalence of DESH among the cohort and compare the surgical outcomes in the presence or absence of DESH. MATERIALS AND METHODS: A retrospective cohort study was conducted at a single institution (Johns Hopkins Hospital) to include patients surgically treated for adult hydrocephalus between 2003 and 2014 drawn from a data base of patients who had undergone standardized hydrocephalus protocol MR imaging. Preoperative imaging was reviewed by 2 blinded neuroradiologists to characterize the presence of DESH. Preoperative and postoperative clinical symptomatology was recorded. Frequencies were compared using the Fisher exact test, and nonparametric means were compared using the Mann-Whitney U Test. RESULTS: One hundred thirty-three subjects were identified and included (96 DESH absent, 37 DESH present). Shunting led to significant improvement in gait and urinary and cognitive symptoms for the overall cohort and for patients with and without DESH (P < .05). The Fisher exact test did not demonstrate any significant differences in either gait or urinary or cognitive symptom improvement between patients with or without DESH (P > .05). CONCLUSIONS: The current study demonstrated symptom improvement in patients with adult hydrocephalus following shunting, with no significant differences between subjects with and without DESH. Thus, shunt insertion for patients with adult hydrocephalus should not rely solely on the presence of preoperative DESH findings.

Contrast-Enhanced CISS Imaging for Evaluation of Neurovascular Compression in Trigeminal Neuralgia: Improved Correlation with Symptoms and Prediction of Surgical Outcomes.

BACKGROUND AND PURPOSE: Thin-section MR imaging through the posterior fossa is frequently used for trigeminal neuralgia. Typical heavily T2-weighted imaging methods yield high anatomic detail and contrast between CSF and neurovascular structures, but poor contrast between vessels and nerves. We hypothesized that the addition of gadolinium-based contrast material to 3D-constructive interference in steady-state imaging would improve the characterization of trigeminal compression. MATERIALS AND METHODS: Retrospective review of high-resolution MRIs was performed in patients without prior microvascular decompression. 3D-CISS imaging without contrast and with contrast for 81 patients with trigeminal neuralgia and 15 controls was intermixed and independently reviewed in a blinded fashion. Cisternal segments of both trigeminal nerves were assessed for the grade of neurovascular conflict, cross-sectional area, and degree of flattening. Data were correlated with symptom side and pain relief after microvascular decompression using the Fisher exact test, receiver operating curve analysis, and a paired t test. RESULTS: Contrast-enhanced CISS more than doubled the prevalence of the highest grade of neurovascular conflict (14.8% versus 33.3%, P = .001) and yielded significantly lower cross-sectional area (P = 8.6 × 10-6) and greater degree of flattening (P = .02) for advanced-grade neurovascular conflict on the symptoms side compared with non-contrast-enhanced CISS. Patients with complete pain relief after microvascular decompression had significantly lower cross-sectional area on contrast-enhanced CISS compared with non-contrast-enhanced CISS on preoperative imaging (P = 2.0 × 10-7). Performance based on receiver operating curve analysis was significantly improved for contrast-enhanced CISS compared with non-contrast-enhanced CISS. CONCLUSIONS: The addition of contrast material to 3D-CISS imaging improves the performance of identifying unilateral neurovascular compression for symptomatic trigeminal neuralgia and predicting outcomes after microvascular decompression.

Detection of the Stellate and Thoracic Sympathetic Chain Ganglia with High-Resolution 3D-CISS MR Imaging.

BACKGROUND AND PURPOSE: Despite the importance of the sympathetic nervous system in homeostasis and its putative role in various disease states, little is known regarding our ability to image the sympathetic chain and sympathetic chain ganglia, perhaps owing to their small size. In this retrospective study, we sought to evaluate the normal anatomy of the sympathetic chain ganglia and assess the detectability of the sympathetic chain and sympathetic chain ganglia on high-resolution 3D-CISS images. MATERIALS AND METHODS: This study included 29 patients who underwent 3D-CISS MR imaging of the thoracic spine for reasons unrelated to abnormalities of the sympathetic nervous system. Patients with a prior spinal operation or visible spinal pathology were excluded. The sympathetic chain ganglia were evaluated using noncontrast 3D-CISS MR imaging. Statistical analyses included t tests and measures of central tendency. The Cohen κ statistic was calculated to evaluate interrater reliability. RESULTS: The stellate ganglion and thoracic chain ganglia were identified in all subjects except at the T10-T11 and T11-T12 levels. The stellate ganglion was found inferomedial to the subclavian artery and anterior and inferior to the transverse process of C7 in all subjects. Thoracic sympathetic chain ganglia were identified ventral to the costovertebral junction in all subjects from T2 to T10. There was strong interobserver agreement for the detection of the sympathetic chain ganglia with κ > 0.80. The size, shape, and location of these structures corresponded with gross anatomic and surgical observations. CONCLUSIONS: The thoracic sympathetic chain ganglia can be identified on precontrast 3D-CISS MR imaging. This technique may aid in the initial evaluation of stellate ganglion and/or sympathetic chain ganglia size and signal change for comparison in future studies.

High-Resolution MRI Findings following Trigeminal Rhizotomy.

BACKGROUND AND PURPOSE: Patients with trigeminal neuralgia often undergo trigeminal rhizotomy via radiofrequency thermocoagulation or glycerol injection for treatment of symptoms. To date, radiologic changes in patients with trigeminal neuralgia post-rhizotomy have not been described, to our knowledge. The aim of this study was to evaluate patients after trigeminal rhizotomy to characterize post-rhizotomy changes on 3D high-resolution MR imaging. MATERIALS AND METHODS: A retrospective review of trigeminal neuralgia protocol studies was performed in 26 patients after rhizotomy compared with 54 treatment-naïve subjects with trigeminal neuralgia. Examinations were reviewed independently by 2 neuroradiologists blinded to the side of symptoms and treatment history. The symmetry of Meckel's cave on constructive interference in steady-state and the presence of contrast enhancement within the trigeminal nerves on volumetric interpolated breath-hold examination images were assessed subjectively. The signal intensity of Meckel's cave was measured on coronal noncontrast constructive interference in steady-state imaging on each side. RESULTS: Post-rhizotomy changes included subjective clumping of nerve roots and/or decreased constructive interference in steady-state signal intensity within Meckel's cave, which was identified in 17/26 (65%) patients after rhizotomy and 3/54 (6%) treatment-naïve patients (P < .001). Constructive interference in steady-state signal intensity within Meckel's cave was, on average, 13% lower on the side of the rhizotomy in patients posttreatment compared with a 1% difference in controls (P < .001). Small regions of temporal encephalomalacia were noted in 8/26 (31%) patients after rhizotomy and 0/54 (0%) treatment-naïve patients (P < .001). CONCLUSIONS: Post-trigeminal rhizotomy findings frequently include nerve clumping and decreased constructive interference in steady-state signal intensity in Meckel's cave. Small areas of temporal lobe encephalomalacia are encountered less frequently.

Neurons in monkey prefrontal cortex that track past or predict future performance.

Although frontal cortex is thought to be important in controlling behavior across long periods of time, most studies of this area concentrate on neuronal responses instantaneously relevant to the current task. In order to investigate the relationship of frontal activity to behavior over longer time periods, we trained rhesus monkeys on a difficult oculomotor task. Their performance fluctuated during the day, and the activity of prefrontal neurons, even measured while the monkeys waited for the targets to appear at the beginning of each set of trials, correlated with performance in a probabilistic rather than a determinist manner: neurons reflected past or predicted future performance, much more than they reflected current performance. We suggest that this activity is related to processes such as arousal or motivation that set the tone for behavior rather than controlling it on a millisecond basis, and could result from ascending pathways that utilize slow, second-messenger synaptic processes.