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Dean Chou, Justin S. Smith and Cynthia T. Chin

✓The authors describe a case of a discal cyst that resolved almost completely without direct intervention. Discal cysts are rare, with the authors of only a few case reports describing this entity. These reports all identify at least some intervention performed for alleviation of the symptoms, including open surgery, minimally invasive surgery, or percutaneous puncture with aspiration. The authors report on a 35-year-old man with radiculopathy who presented with a discal cyst and was treated with a routine epidural injection and selective nerve root block. Within 5 months, the discal cyst showed dramatic regression on magnetic resonance imaging and the patient’s symptoms improved. The natural history of this pathological entity is unknown, and to the authors’ knowledge this is the first detailed report of the regression of a discal cyst without surgery or aspiration.

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Kurtis I. Auguste, Cynthia Chin, Frank L. Acosta and Christopher P. Ames

Object

Expandable cylindrical cages (ECCs) have been utilized successfully to reconstruct the thoracic and lumbar spine. Their advantages include ease of insertion, reduced endplate trauma, direct application/maintenance of interbody distraction force, and one-step kyphosis correction. The authors present their experience with ECCs in the reconstruction of the cervical spine in patients with various pathological conditions.

Methods

Data obtained in 22 patients were reviewed retrospectively. A standard anterior cervical corpectomy was performed in all cases. Local vertebral body bone was harvested for use as graft material. Patients underwent pre- and postoperative assessment involving the visual analog scale (VAS), Nurick grading system for determining myelopathy disability, and radiographic studies to determine cervical kyphosis/lordosis and cage subsidence. Fusion was defined as the absence of motion on flexion–extension x-ray films.

Sixteen patients presented with spondylotic myelopathy, two with osteomyelitis, two with fracture, one with tumor metastasis, and one with severe stenosis. Fourteen patients underwent supplemental posterior spinal fusion, seven underwent single-level corpectomy, and 15 patients underwent multilevel corpectomy. No perioperative complications occurred. The mean follow-up period was 22 months. In 11 patients with preexisting kyphosis (mean deformity +19°), the mean correction was 22°. There was no statistically significant difference in subsidence between single- and multilevel corpectomy or between 360º fusion and anterior fusion alone. The VAS scores improved by 35%, and the Nurick grade improved by 31%. The fusion rate was 100%.

Conclusions

The preliminary results support the use of ECCs in the cervical spine in the treatment of patients with various disease processes. No significant subsidence was noted, and pain and functional scores improved in all cases. Expandable cylindrical cages appear to be well suited for cervical reconstruction and for correcting sagittal malalignment.

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Matthew D. Bucknor, Lynne S. Steinbach, David Saloner and Cynthia T. Chin

Object

Extraspinal sciatica can present unique challenges in clinical diagnosis and management. In this study, the authors evaluated qualitative and quantitative patterns of sciatica-related pathology at the ischial tuberosity on MR neurography (MRN) studies performed for chronic extraspinal sciatica.

Methods

Lumbosacral MRN studies obtained in 14 patients at the University of California, San Francisco between 2007 and 2011 were retrospectively reviewed. The patients had been referred by neurosurgeons or neurologists for chronic unilateral sciatica (≥ 3 months), and the MRN reports described asymmetrical increased T2 signal within the sciatic nerve at the level of the ischial tuberosity. MRN studies were also performed prospectively in 6 healthy volunteers. Sciatic nerve T2 signal intensity (SI) and cross-sectional area at the ischial tuberosity were calculated and compared between the 2 sides in all 20 subjects. The same measurements were also performed at the sciatic notch as an internal reference. Adjacent musculoskeletal pathology was compared between the 2 sides in all subjects.

Results

Seven of the 9 patients for whom detailed histories were available had a specific history of injury or trauma near the proximal hamstring preceding the onset of sciatica. Eight of the 14 patients also demonstrated soft-tissue abnormalities adjacent to the proximal hamstring origin. The remaining 6 had normal muscles, tendons, and marrow in the region of the ischial tuberosity. There was a significant difference in sciatic nerve SI and size between the symptomatic and asymptomatic sides at the level of the ischial tuberosity, with a mean adjusted SI of 1.38 compared with 1.00 (p < 0.001) and a mean cross-sectional nerve area of 0.66 versus 0.54 cm2 (p = 0.002). The control group demonstrated symmetrical adjusted SI and sciatic nerve size.

Conclusions

This study suggests that chronic sciatic neuropathy can be seen at the ischial tuberosity in the setting of prior proximal hamstring tendon injury or adjacent soft-tissue abnormalities. Because hamstring tendon injury as a cause of chronic sciatica remains a diagnosis of exclusion, this distinct category of patients has not been described in the radiographic literature and merits special attention from clinicians and radiologists in the management of extraspinal sciatica. Magnetic resonance neurography is useful for evaluating chronic sciatic neuropathy both qualitatively and quantitatively, particularly in patients for whom electromyography and traditional MRI studies are unrevealing.

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Stephen T. Magill, Marcel Brus-Ramer, Philip R. Weinstein, Cynthia T. Chin and Line Jacques

Neurogenic thoracic outlet syndrome (nTOS) is caused by compression of the brachial plexus as it traverses from the thoracic outlet to the axilla. Diagnosing nTOS can be difficult because of overlap with other complex pain and entrapment syndromes. An nTOS diagnosis is made based on patient history, physical exam, electrodiagnostic studies, and, more recently, interpretation of MR neurograms with tractography. Advances in high-resolution MRI and tractography can confirm an nTOS diagnosis and identify the location of nerve compression, allowing tailored surgical decompression. In this report, the authors review the current diagnostic criteria, present an update on advances in MRI, and provide case examples demonstrating how MR neurography (MRN) can aid in diagnosing nTOS. The authors conclude that improved high-resolution MRN and tractography are valuable tools for identifying the source of nerve compression in patients with nTOS and can augment current diagnostic modalities for this syndrome.

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Cornelia S. von Koch, Geoffrey Young, Cynthia T. Chin and Michael T. Lawton

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Rose Du, Kurtis I. Auguste, Cynthia T. Chin, John W. Engstrom and Philip R. Weinstein

Object

Treatment of spinal and peripheral nerve lesions relies on localization of the pathology by the use of neurological examination, spinal MR imaging and electromyography (EMG)/nerve conduction studies (NCSs). Magnetic resonance neurography (MRN) is a novel imaging technique recently developed for direct imaging of spinal and peripheral nerves. In this study, the authors analyzed the role of MRN in the evaluation of spinal and peripheral nerve lesions.

Methods

Imaging studies, medical records, and EMG/NCS results were analyzed retrospectively in a consecutive series of 191 patients who underwent MRN for spinal and peripheral nerve disorders at the University of California, San Francisco between March 1999 and February 2005. Ninety-one (47.6%) of these patients also underwent EMG/NCS studies.

Results

In those who underwent both MRN and EMG/NCS, MRN provided the same or additional diagnostic information 32 and 45% of patients, respectively. Magnetic resonance neurograms were obtained at a median of 12 months after the onset of symptoms. The utility of MRN correlated with the interval between the onset of symptoms to MRN. Twelve patients underwent repeated MRN for serial evaluation. The decrease in abnormal signal detected on subsequent MRN correlated with time from onset of symptoms and the time interval between MRN, but not with resolution of symptoms. Twenty-one patients underwent MRN postoperatively to assess persistent, recurrent, or new symptoms; of these 3 (14.3%) required a subsequent surgery.

Conclusions

Magnetic resonance neurography is a valuable adjunct to conventional MR imaging and EMG/NCS in the evaluation and localization of nerve root, brachial plexus, and peripheral nerve lesions. The authors found that MRN is indicated in patients: 1) in whom EMG and traditional MR imaging are inconclusive; 2) who present with brachial plexopathy who have previously received radiation therapy to the brachial plexus region; 3) who present with brachial plexopathy and have systemic tumors; and 4) in patients under consideration for surgery for peripheral nerve lesions or after trauma. Magnetic resonance neurography is limited by the size of the nerve trunk imaged and the timing of the study.

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Yaping Joyce Liao, William P. Dillon, Cynthia T. Chin, Michael W. McDermott and Jonathan C. Horton

✓The authors describe a newly recognized complication of lumboperitoneal (LP) shunt placement, namely, intracranial hypotension from leakage of cerebrospinal fluid (CSF) through a defect in the lumbar dura created by the shunt catheter. They report on a 47-year-old obese woman with idiopathic intracranial hypertension who underwent routine placement of an LP shunt. Following surgery, her headache became worse. Two radionuclide shunt studies showed no anterograde tracer flow, suggesting either obstruction or a leak. After shunt reservoir manometry indicated low pressure, spinal magnetic resonance (MR) imaging was performed. The MR images revealed a CSF leak from the lumbar thecal sac. A computed tomography (CT) myelogram, performed by injection into the shunt reservoir, confirmed the presence of a leak by showing extravasation of contrast agent into the epidural space. The patient was treated by application of a CT-guided blood patch at the leak site. Catheter-associated CSF leak is an unusual cause of intracranial hypotension that can occur following LP shunt placement. This case report outlines the clinical features of this condition, documents the neuroradiological findings, and demonstrates successful treatment with a blood patch.

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Cheerag D. Upadhyaya, Jau-Ching Wu, Cynthia T. Chin, Gopalakrishnan Balamurali and Praveen V. Mummaneni

Object

The accurate intraoperative localization of the correct thoracic spine level remains a challenging problem in both open and minimally invasive spine surgery. The authors describe a technique of using preoperatively placed percutaneous fiducial screws to localize the area of interest in the thoracic spine, and they assess the safety and efficacy of the technique.

Methods

To avoid wrong-level surgery in the thoracic spine, the authors preoperatively placed a percutaneous 5-mm fiducial screw at the level of intended surgery using CT guidance. Plain radiographs and CT images with reconstructed views can then be referenced in the operating room to verify the surgical level, and the fiducial screw is easily identified on intraoperative fluoroscopy. The authors compared a group of 26 patients who underwent preoperative (often outpatient) fiducial screw placement prior to open or minimally invasive thoracic spine surgery to a historical group of 26 patients who had intraoperative localization with fluoroscopy alone.

Results

In the treatment group of 26 patients, no complications related to fiducial screw placement occurred, and there was no incidence of wrong-level surgery. In comparison, there were no wrong-level surgeries in the historical cohort of 26 patients who underwent mini-open or open thoracic spine surgery without placement of a fiducial screw. However, the authors found that the intraoperative localization fluoroscopy time was greatly reduced when a fiducial screw localization technique was employed.

Conclusions

The aforementioned technique for intraoperative localization is safe, efficient, and accurate for identifying the target level in thoracic spine exposures. The fiducial marker screw can be placed using CT guidance on an outpatient basis. There is a reduction in the amount of intraoperative fluoroscopy time needed for localization in the fiducial screw group.

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Frank L. Acosta Jr., Cynthia T. Chin, Alfredo Quiñones-Hinojosa, Christopher P. Ames, Philip R. Weinstein and Dean Chou

Establishing the diagnosis of cervical osteomyelitis in a timely fashion is critical to prevent catastrophic neurological injury. In the modern imaging era, magnetic resonance imaging in particular has facilitated the diagnosis of cervical osteomyelitis, even before the onset of neurological signs or symptoms. Nevertheless, despite advancements in diagnosis, disagreement remains regarding appropriate surgical treatment. The role of instrumentation and type of graft material after cervical decompression remain controversial. The authors describe the epidemiological features, pathogenesis, and diagnostic evaluation, and the surgical and nonsurgical interventions that can be used to treat osteomyelitis of the cervical spine. They also review the current debate about the role of instrumentation in preventing spinal deformity after surgical decompression for cervical osteomyelitis. Based on this review, the authors conclude that nonsurgical therapy is appropriate if neurological signs or symptoms, instability, deformity, or spinal cord compression are absent. Surgical decompression, debridement, stabilization, and deformity correction are the goals once the decision to perform surgery has been made. The roles of autogenous graft, instrumentation, and allograft have not been clearly delineated with Class I data, but the authors believe that spinal stability and decompression override creating an environment that can be completely sterilized by antibiotic drugs.

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Neil G. Simon, Tene Cage, Jared Narvid, Roger Noss, Cynthia Chin and Michel Kliot

The goals of the present study were to demonstrate the ability of high-resolution ultrasonography to delineate normal nerve fascicles within or around peripheral nerve sheath tumors (NSTs). A blinded examiner evaluated 2 patients with symptomatic upper limb NSTs with high-resolution ultrasonography performed in the perioperative suite using a portable ultrasonography system. Ultrasonographic examinations located the tumor mass and identified the normal nerve fascicles associated with the mass. The locations of normal nerve tissue were mapped and correlated with results of MR tractography, operative inspection, and intraoperative electrophysiological monitoring. The study demonstrated a close correlation between normal nerve fascicles identified by ultrasonography, MR tractography, and intraoperative electrophysiological mapping. In particular, ultrasonographic examinations accurately identified the surface regions of the tumor without overlying normal nerve tissue. These preliminary data suggest that preoperative ultrasonographic examinations may provide valuable information, supplementary to the information obtained from intraoperative electrophysiological monitoring. Identification of normal nerve tissue prior to surgery may provide additional information regarding the risk of iatrogenic nerve injury during percutaneous tumor biopsy or open resection of the tumor and may also aid in selecting the optimum surgical approach.