(Cost-)effectiveness of lower extremity nerve decompression surgery in subjects with diabetes: the DeCompression (DECO) trial-study protocol for a randomised controlled trial.

INTRODUCTION: The peripheral nerves of patients with diabetes are often pathologically swollen, which results in entrapment at places of anatomical narrowing. This results in nerve dysfunction. Surgical treatment of compression neuropathies in the lower extremities (lower extremity nerve decompression (LEND)) results in relief of symptoms and gain in peripheral nerve function, which may lead to less sensory loss (short term) and less associated detrimental effects including foot ulceration and amputations, and lower costs (long term). The aim of the DeCompression trial is to evaluate the effectiveness and (cost-)effectiveness of surgical decompression of compressed lower extremity nerves (LEND surgery) compared with patients treated with conventional (non-surgical) care. METHODS AND ANALYSIS: A stratified randomised (1 to 1) controlled trial comparing LEND surgery (intervention) with conventional non-surgical care (control strategy) in subjects with diabetes with problems of neuropathy due to compression neuropathies in the lower extremity. Randomisation is stratified for participating hospital (n=11) and gender. Patients and controls have the same follow-up at 1.5, 3, 6, 9, 12, 18, 24 and 48 months. Participants (n=344) will be recruited in 12 months and enrolled in all affiliated hospitals in which they receive both the intervention or conventional non-surgical care and follow-up. Outcome assessors are blinded to group assignment. PRIMARY OUTCOME: disease-specific quality of life (Norfolk Quality of Life Questionnaire-Diabetic Neuropathy). SECONDARY OUTCOMES: health-related quality of life (EuroQoL 5-dimension 5-level (EQ-5D5L), 36-item Short Form (SF-36)), plantar sensation (Rotterdam Diabetic Foot Test Battery), incidence of ulcerations/amputations, resource use and productivity loss (Medical Cost Questionnaire, Productivity Cost Questionnaire) during follow-up. The incremental cost-effectiveness ratio will be estimated on the basis of the collected empirical data and a cost-utility model. ETHICS AND DISSEMINATION: Ethics approval has been granted by the Medical Research Ethics Committee of Utrecht University Medical Center (reference: NL68312.041.19v5, protocol number: 19-335/M). Dissemination of results will be via journal articles and presentations at national and international conferences. TRIAL REGISTRATION NUMBER: NetherlandsTrial Registry NL7664.

Assessment of Optic Pathway Structure and Function in Patients With Compression of the Optic Chiasm: A Correlation With Optical Coherence Tomography.

PURPOSE: The purpose of this study was to investigate correlations between retinal fiber thickness measured by optical coherence tomography (OCT) and anterograde functional and structural differences in the optic pathway of patients with compression of the optic chiasm. Our hypothesis was that loss of visual acuity caused by chronic compressive pathologies may lead to an irreversible decline in vision because of permanent neurodegeneration of the optic radiations and visual cortex. METHODS: Quantitative OCT, functional magnetic resonance imaging (MRI) and diffusion tensor MRI measurements were made in 17 patients being surgically treated for chiasmal compression. RESULTS: In our study we found that surgically irreversible visual field defects and reduced retinal nerve fiber layer thickness were significantly associated with lower fractional diffusion anisotropy and higher diffusivities in optic radiations and less functional MRI activation in the visual cortex. CONCLUSIONS: Damage to the retinal nerve fiber layer is associated with downstream structural and functional degradation of the optic pathway. This may be related to trans-synaptic degeneration and the fact that these factors are important potential imaging biomarkers for predicting visual recovery after surgical decompression.

Rationale, Science, and Economics of Surgical Nerve Decompression for Diabetic Neuropathy Foot Complications.

Nerve decompression is effective and safe for dealing with the pain and numbness symptoms of the frequent nerve compression entrapments in diabetic symmetric peripheral neuropathy (DSPN). Evidence has accumulated of balance and stability improvements and protection against diabetic foot ulceration, recurrence and its complication cascade. Nerve decompression proffers significant benefit versus the large socioeconomic costs of DSPN complications. Advancing understanding of the mechanism of nerve compression and altered axonal activity in diabetes clarifies the basis of clinical benefit. Clinicians should seek out and recognize nerve entrapments and consider advising nerve decompression for relief of DSPN symptoms and prevention of complications.

Current status: new technologies for the treatment of patients with fecal incontinence.

Fecal incontinence is a frequent and debilitating condition that may result from a multitude of different causes. Treatment is often challenging and needs to be individualized. During the last several years, new technologies have been developed, and others are emerging from clinical trials to commercialization. Although their specific roles in the management of fecal incontinence have not yet been completely defined, surgeons have access to them and patients may request them. The purpose of this project is to put into perspective, for both the patient and the practitioner, the relative positions of new and emerging technologies in order to propose a treatment algorithm.

Three-dimensional assessment of hand outcome.

INTRODUCTION: Patient reported outcome measures are central to National Health Service quality of care assessments. This study investigated the benefit of elective hand surgery by the simultaneous analysis of pain, function and appearance, using a three-dimensional (3D) graphical model for evaluating and presenting outcome. METHODS: A total of 188 patients scheduled for surgery completed pre- and postoperative questionnaires grading the severity of their pain, dysfunction and deformity of their hand(s). Scores were plotted on a 3D graph to demonstrate the degree of 'normalisation' following surgery. RESULTS: Surgical groups included: nerve compression (n=53), Dupuytren's disease (n=51), trigger finger (n=20), ganglion (n=17) or other lump (n=21), trapeziometacarpal joint osteoarthritis (n=10), rheumatoid disease (n=5) and other pathology (n=13). A significant improvement towards normality was seen after surgery in each group except for patients with rheumatoid disease. CONCLUSIONS: This study provides a simple, visual representation of hand surgery outcome by plotting patient scores for pain, function and appearance simultaneously on a 3D graph.

Evaluation of early visual recovery in pituitary macroadenomas after endoscopic endonasal transphenoidal surgery: Quantitative assessment with diffusion tensor imaging (DTI).

BACKGROUND: Visual field analyses reflect the degree of the compression to the optic nerve that results the structural damage of the nerve. These structural damages can be evaluated by diffusion tensor imaging (DTI), which assesses the structural integrity of white matter tracts. Thus, we evaluated the quantitative assessment of early visual recovery in patients with pituitary macroadenomas, corresponding DTI with visual field analyses. METHODS: Seventy-two patients who had pituitary macroadenomas with visual field defects were included in the study retrospectively. All patients were operated on by pure endoscopic transphenoidal approach. Visual field assessment using Humphrey field analyzer and DTI with 3T magnet were performed in the preoperative and postoperative second day and sixth month. FINDINGS: Mean symptom duration was 14.7 ± 10.5 weeks in the full recovery group patients, 50.1 ± 29.1 weeks in partial recovery patients, and 92.4 ± 15.4 weeks in the ones with no recovery. There was a significant difference at p < 0.001 among the groups. On visual field analysis, the visual lost was mostly recognized at upper temporal levels preoperatively. Visual field findings of both eyes were improved in 80% of the patients. Among these, 25% revealed full recovery, 55.6% partial recovery, and 19.4% did not demonstrate significant changes. DTI assessments of affected sides revealed preoperative fractional anisotropy (FA) values below 0.400 and mean diffusivity (MD) values over 1,400 × 10(-6) mm(2) s(-1) were related with no visual improvement in the postoperative 6 months period. The percentage increase of mean FA values of the affected areas postoperatively were found to be 21.9% in totally responded patients, 20.6% in partial responded patients, and 9.8% in patients that did not respond. CONCLUSIONS: There is a correlation between DTI-derived FA values of the optic nerves and visual parameters. DTI assessments of the affected sides with FA and MD values may help to estimate the response of visual improvement to the surgical therapy in the early postoperative period.

Assessment of processed porcine extracellular matrix as a protective barrier in a rabbit nerve wrap model.

Nerve wrapping can improve outcomes by protecting nerves in a scarred tissue bed. Autologous tissue wraps have shown good results, but there are limitations associated with harvesting and availability. Extracellular matrix (ECM) derived from porcine small intestinal submucosa offers an attractive off-the-shelf option. This study evaluated this material as a nerve wrap. The sciatic nerves of 18 New Zealand rabbits were exposed and then wrapped, while the contralateral side served as sham control. Presence and quality of adhesions, motor conduction velocity (MCV), and histology were evaluated at 1, 2, and 6 months ( N = 6 animals per time point). The quality, extent, tenacity, and overall impression of adhesions were not different from control at any time point ( P = 0.18 to 0.99). MCV was also not statistically different from control (1 month, P = 0.35; 2 months, P = 0.20; 6 months, P = 0.83). Histology demonstrated that wrapped nerves were healthy in terms of myelination, density, and vascularity compared with controls. Vascularization and incorporation of the ECM material could be visualized at explants. All assessments supported the feasibility and safety of this material as a nerve wrap. Its ability to function as a protective barrier has strong implications for clinical use in trauma and/or recurrent compression neuropathies.

[The ultrasound assessment of neuro-muscular apparatus by the radial nerve injuries].

The use of ultrasound (US) scanning to assess the muscular function during the reinnervation is a new concept in medicine. The US signs of muscle denervation were thoroughly described in the article. The US muscle monitoring was performed by the complete and partial radial nerve injury in various follow-up periods. Absolute and relative indications for surgery were determined. The comparative characteristics of structural muscular changes, together with the US test for the assessment of the treatment efficacy and nerval and muscular recovery were suggested.

Incidence, management, and prognosis of early ulnar nerve dysfunction in type C fractures of distal humerus.

BACKGROUND: Displaced comminuted of the distal humerus in adults are among the most complex fractures to be managed effectively. The ulnar nerve is at high risk of impingement secondary to injury, operation, and postoperative rehabilitation in these fractures. In this study we focus on the incidence, management, and prognosis of early ulnar nerve dysfunction in the course of treating type C fractures of distal humerus. METHODS: We examine a patient sample of 117 consecutive AO type C fractures of distal humerus, between June 1998 and October 2005. Twenty-nine patients exhibited preoperative ulnar nerve compression symptoms (incidence 24.8%) and were divided into two groups randomly, which received treatment of anterior subfascial transposition or in situ decompression of the ulnar nerve respectively, in conjunction with internal fixation with medial and lateral plates. RESULTS: The subgroup of 88 patients without preoperative ulnar nerve symptoms remained asymptomatic postoperatively (0% incidence of late ulnar nerve dysfunction). According to Bishop rating system, excellent and good results of ulnar nerve function were achieved in 13 of 15 patients (86.7%) in the transposition group, 8 of 14 patients (57.1%) in the in situ decompression group. The results difference is statistically significant (p < 0.05). CONCLUSIONS: We conclude that neurolysis and anterior subfascial transposition of vascularized ulnar nerve during open reduction and internal fixation of type C fractures of the distal humerus is beneficial in cases of early ulnat nerve dysfunction.

Caudal compression of the infraorbital nerve: a novel surgical technique for treatment of idiopathic headshaking and assessment of its efficacy in 24 horses.

UNLABELLED: REASONS FOR DESIGNING AND REPORTING TECHNIQUE: Idiopathic headshaking has remarkable similarities to human neuropathic facial pain syndromes associated with post herpetic and trigeminal neuralgia. These derive from abnormal sensory function within the peripheral or central pathways of the trigeminal nerve (TgN). Limiting input from the TgN can be helpful in controlling the perception of pain. Rhizotomy of the infraorbital branch of the TgN as it emerges from the infraorbital canal has been reported but has a poor efficacy. A novel technique involves compression of the nerve at a more caudal location within the infraorbital canal and the technique requires validation. HYPOTHESIS: Caudal compression of the infraorbital nerve with platinum coils, performed in horses diagnosed with idiopathic headshaking, results in a decrease in clinical signs. METHODS: Caudal compression of the infraorbital nerve, using platinum embolisation coils, was performed under fluoroscopic guidance. Clinical records of 24 idiopathic headshakers that had undergone this procedure were reviewed. Follow-up information was obtained by telephone questionnaire with the owner or referring veterinary surgeon. RESULTS: All 24 horses had at least one surgical procedure. Median follow-up time was 6 months. There were 2 horses which had surgery 2 weeks before follow-up and these were excluded from the analysis of outcome. Following one surgery, 13/22 horses (59.0%) had a successful outcome. Of the 9 horses that did not improve, surgery was repeated in 6 cases. Two of these horses had a successful outcome. Overall, a successful outcome was obtained in 16/19 horses (84.2%). CONCLUSIONS: This surgical technique is likely to prevent input from the TgN at a more caudal location then the previously described infraorbital neurectomy. The technique requires refinement.

[Emergency scenario: cauda equina syndrome--assessment and management]. / Notfallszenario: Cauda-equina-Syndrom--Beurteilung und Management.

Acute low back pain is one of the most frequent reason for an emergency or primary care physician visit. Up to 90% of all adults will experience an episode of back pain at some point during their lifetime. Although the majority of patients have uncomplicated benign presentation and 80-90% recover within 4 to 6 weeks, there is a small subset who has an underlying potential life-threatening etiology. Among them are aortic dissection, ruptured abdominal aortic aneurysm, vertebral osteomyelitis, spinal epidural abscess and the cauda equina syndrome (CES). The latter entails a compression of the nerve roots of the cauda equina. These patients usually present post-traumatically with the clinical triad of saddle anesthesia, bowel or bladder dysfunction and muscular weakness of the lower extremeties. A delayed diagnosis can result in a significantly increased morbidity. Therefore, early diagnosis and the initiation of the appropriate therapeutic steps are essential. A thourough anamnesis and physical examination are leading to the suspected diagosis. Below, clinical presentation, diagnosis and relevant treatment of the CES are discussed.

Long term results of radial tunnel release--the effect of co-existing tennis elbow, multiple compression syndromes and workers' compensation.

SUMMARY: Surgical decompression of radial tunnel syndrome (RTS) remains controversial because the results are unpredictable. This study is a retrospective analysis of the long term outcomes of RTS release and a comparison of our findings with previous studies. Thirty-three extremities in 31 patients underwent decompression for radial tunnel syndrome between 1994 and 2003, of which 27 extremities in 25 patients were available for long term follow up after an average of 57 months (range 16 to 106 months). Outcomes were evaluated using the criteria of Ritts et al. (1987). For 16 patients (18 of 27 extremities), the outcome was rated as good (67%), for four patients (four extremities) as fair (15%), and for five patients (five extremities) as poor (18%). The outcome was better in patients with simple RTS (86% good results) compared with patients with additional nerve compression syndromes (57% good results), or patients with coexisting lateral epicondylitis (70% vs 43% good results), or patients who were receiving workers' compensation (73% vs 58% good results). One-third of patients still had moderate or severe disability which affected their ability to work, but 82% had relief of their pain. Surgical decompression is therefore beneficial for simple RTS, but may be less successful if there are co-existing additional nerve compression syndromes or lateral epicondylitis or if the patient is receiving workers'compensation.

The surgical management of metastatic spinal disease: prospective assessment and long-term follow-up.

The last decade has witnessed a resurgence of interest in the surgical treatment of metastatic spinal disease to compliment radiotherapy. A recent randomized controlled trial looking directly at this issue concluded strongly in favour of a combination of surgical decompression and radiotherapy, and there is now growing enthusiasm for surgery to play a role in the management of these patients. We present a prospective cohort study of 62 patients who presented with metastatic cord or cauda equina compression, and were treated with surgical decompression and fixation where necessary. Patients were treated by one surgeon working in a single unit. They were followed-up long term and were assessed objectively, by clinical assessment and prospective questionnaires that included SF36, visual analogue pain scores and Roland Morris back pain scores. Sixty-two patients with a median age of 62 (22-79 years, 27 male) were included in the study. The commonest primary tumours were breast (26%) and lymphoma (13%). The majority of patients had involvement of thoracic vertebrae (58%). 56% of patients were alive at 1 year and 28% at 3 years, with significant improvements observed in both walking and continence. Similarly, significant improvements were seen in SF36 quality of life scores as well as pain. With careful patient selection, long-term survival and good quality of life can be achieved. However, not every patient is suitable or appropriate for surgery, and the discussion focuses on where the surgical threshold should be set.

Large ophthalmic segment aneurysms with anterior optic pathway compression: assessment of anatomical and visual outcomes after endosaccular coil therapy.

OBJECT: The optimal therapy for ophthalmic segment aneurysms with anterior optic pathway compression (AOPC) is undecided. Surgical results have been described, but the results of endovascular coil therapy have not been well documented. METHODS: The authors retrospectively reviewed data obtained in all patients who harbored unruptured ophthalmic segment aneurysms with AOPC who underwent endovascular coil therapy at their institution. They analyzed baseline and outcome visual function, aneurysm features, extent of aneurysm closure, internal carotid artery (ICA) occlusion, additional interventions, and neurological outcome. In 17 patients (16 women), age 38 to 83 years, there were 28 affected eyes. All aneurysms were greater than 10 mm in diameter. In the initial procedures 16 of 17 patients received endosaccular coils and the ICA was preserved; in one patient the aneurysm was trapped and the ICA occluded. Patients then underwent follow up for a mean of 2.90 years (range 1 month-1 1.2 years) after the last procedure. One patient died of subarachnoid hemorrhage (SAH) 1 month postoperatively and thus no follow-up data were available for this case. Vision worsened in six patients, stabilized in four, and improved in six. Twelve patients underwent 13 subsequent procedures, including endovascular ICA occlusion in seven, repeated coil therapy in five, and optic nerve decompression in one; vision improved in 83% of these cases after ICA occlusion. A second patient died of SAH 5 months after repeated coil treatment. At the final follow up, vision had improved in eight patients (50%), stabilized in four (25%), and worsened in four (25%). In 16 patients with follow-up studies, aneurysm closure was complete in eight (50%) and incomplete in eight (50%). CONCLUSIONS: The authors found that in patients with ophthalmic segment aneurysms causing chronic AOPC, endosaccular platinum coil therapy, with ICA preservation, may not benefit vision and that additional procedures may be needed. Evaluation of their results suggests that endovascular trapping of the aneurysm and sacrifice of the ICA appear to result in good visual, clinical, and anatomical outcomes.

[Assessment of neurovascular compression in patients with trigeminal neuralgia with a boundary fusion three-dimensional magnetic resonance cisternogram/angiogram].

Precise assessment of the complex nerve-vessel relationship at the root entry zone (REZ) the trigeminal nerve is useful for the planning of the microvascular decompression (MVD) in patients with trigeminal neuralgia. We have applied a boundary imaging of fusion three-dimensional (3D) magnetic resonance (MR) cisternogram/angiogram. The boundary imaging allows virtual assessment of the spatial relationship of the neurovascular compression at the REZ of the trigeminal nerve. The boundary images depicted complex anatomical relationship of the offending vessels to the trigeminal nerve REZ. The presence of offending vessels, compressive site, and degree of neurovascular compression were assessed from various viewpoints in thl cistern and virtually through the brainstem and trigeminal nerve per se. The 3D visualization of the nerve-vessel relationship with fusion images was consistent with the intraoperative findings. The boundary fusion 3D MR cisternogram/angiogram may prove a useful adjunct for the diag nosis and decision-making process to execute the MVD in patients with trigeminal neuralgia.

Fusion imaging of three-dimensional magnetic resonance cisternograms and angiograms for the assessment of microvascular decompression in patients with hemifacial spasms.

OBJECT: The precise preoperative assessment of the complex nerve-vessel relationship at the root exit zone (RExZ) of the facial nerve is important when planning microvascular decompression (MVD) in patients with hemifacial spasms. The authors have developed an imaging technique-the fusion of 3D magnetic resonance (MR) cistemography and coregistered 3D MR angiography images-that allows clear visualization of the spatial relationship between the vessels and the rootlet of the facial nerve at the brainstem. METHODS: The authors reconstructed 3D MR cisternograms and 3D MR angiograms by using a perspective volume-rendering algorithm that they applied to the volumetric data sets of the following modalities: MR cisternography (a T,-weighted 3D fast spin echo sequence) and coregistered MR angiography (a 3D time-of-flight sequence). The complex anatomical relationship between the offending vessels and the facial nerve RExZ was inspected preoperatively by examining the fusion images from various perspectives within the cerebellopontine angle cistern, within the affected facial nerve, and through the simulated surgical route. The reconstructed 3D findings of the nerve-vessel relationship were compared with the intraoperative findings. Postoperatively, the fused 3D MR imaging technique was used to confirm that microsurgical dissection and the interposed prosthesis had succeeded in maintaining the causative vessels in a position away from the RExZ. CONCLUSIONS: The fusion of 3D MR cisternograms and 3D MR angiograms may prove useful in the pre- and postoperative assessment of MVD in patients with hemifacial spasm.

Surgical treatment of symptomatic osteochondroma. A three- to eight-year follow-up study.

Our aim was to investigate the outcome of excision ofosteochondromas. Between 1994 and 1998, 92 symptomatic osteochondromas in 86 patients were excised. There were 40 women and 46 men with a mean age of 20 years (3 to 62). Of these, 56 had a solitary osteochondroma and 30 had multiple hereditary tumours. The presenting symptoms were pain (79.1%), swelling (23.3%), reduced range of movement (19.8%), cosmetic abnormalities (17.4%), and bursitis (12.8%). The most common site (37.6%) was around the knee. Four patients had major complications (4.7%) including one intra-operative fracture of the femoral neck and three nerve palsies which resolved after decompression. Six patients had minor complications. Overall, 93.4% of the preoperative symptoms resolved after excision of the tumours. Excision is a successful form of treatment for symptomatic osteochondromas with a low morbidity.

[Functional assessment before and after interventions on the optic chiasm system]. / Funktionelle Befunde vor und nach Eingriffen am optochiasmalen System.

OBJECTIVES: In the course of a tumor in the area of the optic chiasm the optochiasmal system is often exposed to compressive and vascular irritations. This study deals with the functional results (visual acuity and visual field) before and after surgery based on the primary situation and morphology of the tumor in order to give a prognosis on this matter. METHODS: 62 patients (41 female, 21 male) suffering from tumors in the area of the optic chiasm were retrospectively reviewed. The duration of the follow-up was an average of 25.82 months, +/- 20.04. Among the tumors investigated there were 36 pituitary adenomas, 20 meningiomas, 4 craniopharyngiomas, one histiozytosis X and one gangliozytoma. For visual field examination the Humphrey Field Analyzer, program 30-2, was used. 34 tumors (54.8%) were excised by the transsphenoidal approach, 28 patients (45.2%) underwent transcranial surgery. RESULTS: As for visual acuity, of the 124 eyes 53 eyes (42.8%) improved after surgery, 64 eyes (51.6%) remained unchanged, 7 eyes (5.6%) deteriorated. Of the patients who underwent transsphenoidal surgery, 28 eyes (41.2%) improved after operation, 36 eyes (52.9%) remained unchanged, and 4 eyes (5.9%) worsened. In case of transcranial surgery, 25 eyes (44.6%) improved, 28 eyes (50.0%) remained unchanged, whereas 3 eyes (5.4%) worsened. There was a postoperative improvement in 53.2% of the visual fields, 37.1% remained unchanged, whereas 9.7% deteriorated. CONCLUSION: Both the transsphenoidal and transcranial approaches showed excellent visual outcome. Our experience indicates an excellent prognosis for improvement of visual acuity and visual fields provided an adequate procedure. Results depend, however, on the primary functional and morphological situation. In the case of a large supra-/parasellar tumor component a postoperative deterioration of vision may occur.

Preoperative assessment of trigeminal neuralgia and hemifacial spasm using constructive interference in steady state-three-dimensional Fourier transformation magnetic resonance imaging.

Results of microvascular decompression (MVD) for trigeminal neuralgia (TN) and hemifacial spasm (HFS) may be improved by accurate preoperative assessment of neurovascular relationships at the root entry/exit zone (REZ). Constructive interference in steady state (CISS)-three-dimensional Fourier transformation (3DFT) magnetic resonance (MR) imaging was evaluated for visualizing the neurovascular relationships at the REZ. Fourteen patients with TN and eight patients with HFS underwent MR imaging using CISS-3DFT and 3D fast inflow with steady-state precession (FISP) sequences. Axial images of the cerebellopontine angle (CPA) obtained by the two sequences were reviewed to assess the neurovascular relationships at the REZ of the trigeminal and facial nerves. Eleven patients subsequently underwent MVD. Preoperative MR imaging findings were related to surgical observations and results. CISS MR imaging provided excellent contrast between the cranial nerves, small vessels, and cerebrospinal fluid (CSF) in the CPA. CISS was significantly better than FISP for delineating anatomic detail in the CPA (trigeminal and facial nerves, petrosal vein) and abnormal neurovascular relationships responsible for TN and HFS (vascular contact and deformity at the REZ). Preoperative CISS MR imaging demonstrated precisely the neurovascular relationships at the REZ and identified the offending artery in all seven patients with TN undergoing MVD. CISS MR imaging has high resolution and excellent contrast between cranial nerves, small vessels, and CSF, so can precisely and accurately delineate normal and abnormal neurovascular relationships at the REZ in the CPA, and is a valuable preoperative examination for MVD.