A Capacitive Feedback Transimpedance Amplifier with a DC Feedback Loop Using a Transistor for High DC Dynamic Range.

This study proposes a capacitive feedback transimpedance amplifier (CF-TIA) using a transistor in the direct current (DC) feedback loop for high DC dynamic range. In some applications, the background DC input can vary widely from the minimum to the maximum, and TIA have to sense the target signal even on the top of the maximum DC input. In a conventional CF-TIA, however, the allowable DC input is constrained by the value of the resistor in the DC feedback loop. To allow a fairly high DC input, the resistor is set to a very low value. This causes the thermal noise current to increase significantly. The increased thermal noise is always present even in the minimum DC input, thus degrading the overall noise performance. The circuit proposed herein overcomes this shortcoming by using the transistor instead of the resistor. The adverse effect of the parasitic capacitance of the transistor on system stability is compensated for as well. Then, the analyses of the overall frequency response and design parameters, including the cut-off frequency and attenuation ratio associated with system stability, are presented for the proposed circuit. In addition, in order to cope with the problem that stability is dependent on the amount of DC input, a simple method for ensuring system stability regardless of DC component value is introduced. The presented analyses and the method are generalized for all CF-TIA applications.

Acute burst fracture in Kummell's disease with acute onset neurological deficit: a case report on role of spinal stability and technical notes on "pivot ligamentotaxis".

BACKGROUND: Kummell's Disease has insidious progression. Neurological deficit is usually slow in onset and progression and only few cases of acute neurological deficit have been reported. We came across a case of Kummell's disease which progressed to burst fracture, developed neurological deficit within two weeks. We managed patient with "pivot ligamentotaxis" and Polymethylmethacrylate augmented, posterior compressed, short segment percutaneous pedicle screw fixation. CASE PRESENTATION: Eighty-three years old woman following fall was on conservative management at another hospital. She had no neurological deficit. A week later her back pain aggravated and two weeks later developed bilateral buttock pain, bilateral lower limb weakness and diminished sensation in the sacral area. Radiological investigations (X-rays, Magnetic resonance imaging and Computed tomography) showed L1 vertebral body fracture with vacuum cleft and fracture fragment retropulsed into the spinal canal. A diagnosis of Kummell's disease with burst fracture of L1 vertebra & neurological deficit was made. Patient was managed with Polymethylmethacrylate augmented, posterior compressed, short segment percutaneous pedicle screw fixation. The reduction of the retropulsed fragment was achieved by virtue of "Pivot ligamentotaxis". The patient got relieved of the symptoms (Preoperative VAS 8 and postoperative VAS 3) and was allowed brace assisted ambulation on first postoperative day. CONCLUSION: This study reports acute occurrence of the burst fracture in unstable vertebra inflicted by Kummell's disease and role of spinal stability in recovery. We achieved closed reduction of the fracture fragments and relief of the cord compression by posterior compression with "pivot ligamentotaxis".

Optimal treatment of leptomeningeal spread in glioblastoma: analysis of risk factors and outcome.

BACKGROUND: Glioblastoma (GBM) is the most common and malignant brain tumor in adults. Despite therapeutic advances, almost all patients eventually experience tumor recurrence. Leptomeningeal spread (LMS) is not a rare condition of recurrence. However, the standard management protocol of LMS has not been established. The aim of this study is to report the risk of (LMS) and the prognosis between treatment modalities in GBM patients. METHODS: A retrospective review was conducted of 321 patients who were diagnosed with GBM between January 2006 and December 2010. In 75 patients, LMS of tumor was detected by magnetic resonance image and/or cerebrospinal fluid cytology. Twelve patients underwent intrathecal methotrexate (IT-MTX) chemotherapy. Twenty-two patients underwent other salvage treatments. Forty-one patients underwent conservative management. We analyzed the possible clinical factors for LMS. Further, we examined overall survival and survival after diagnosis of LMS for several treatment modalities. RESULTS: In patients without LMS, median overall survival was 479 days, whereas that in patients with LMS it was 401 days. Younger age and larger initial tumor size were related to more frequent LMS incidence. Proximity between tumor margin and ventricle did not affect LMS. However, median duration from initial diagnosis to LMS was significantly different according to the distance to the ventricle. IT-MTX group's overall survival was 583 days, which is statistically no longer than that of the other treatment group and the conservative management group. However, an additional survival benefit may exist compared to the conservative treatment. The median survival of the IT-MTX group was 181 days compared with 91 days for the conservative management group. CONCLUSIONS: Treatment of LMS is mainly palliative. IT-MTX is generally the first-line treatment modality of LMS. Prediction and prevention of LMS is crucial because its treatment has been limited. Further approaches to improve the therapeutic effect should be established.

Management of Root-Level Double Crush: Case Report with Technical Notes on Contralateral Interlaminar Foraminotomy with Full Endoscopic Uniportal Approach.

BACKGROUND: Double crush of a nerve at the root level is not common. We describe here a double crush of the right L4 nerve with foramina to far lateral disk (ventral) and extraforaminal (dorsal) compression. The double crush was managed by endoscopy with a contralateral uniportal approach from the left interlaminar space. Right lateral recess stenosis at the same level was subsequently managed with the same approach. CASE DESCRIPTION: A 79-year-old lady presented to our clinic with a low backache, right leg pain, and weakness. On her right side, the straight leg raise test was 70 degrees, great toe dorsiflexion was grade 3/5, and hypoesthesia was present in the L4 dermatome. Her preoperative visual analog scale score was 9. Magnetic resonance imaging showed right lateral recess stenosis and a double compression of L4 nerve root from the dorsal and ventral sides. A diagnosis of right lateral recess stenosis with double crush of the right L4 nerve root was made. The patient was managed with percutaneous endoscopic contralateral interlaminar foraminotomy from the left interlaminar approach. She got relief for the symptoms and her postoperative visual analog scale score was 2. Magnetic resonance imaging and computed tomography showed nerve root decompression and well-preserved facet joints. CONCLUSIONS: We conclude that the management of double crush at the nerve root level with interlaminar contralateral approach endoscopy (percutaneous endoscopic contralateral interlaminar foraminotomy) can deal with the issue effectively with facet joint preservation and other benefits of the minimally invasive spine procedure.

Endoscopic Resection of Symptomatic Cervical Facet Cyst in Ankylosing Spondylitis.

BACKGROUND: Extradural benign cysts located in close proximity to the facet joints are called juxtafacetal cysts. Only about 3.5% of such cysts occur in the cervical spine. To our knowledge, there has been no published article on the endoscopic resection of a cervical facet cyst, and this is the first report. CASE DESCRIPTION: A 48-year-old male presented with a chief complaint of severe axial neck pain (visual analog scale score 9) and right scapular pain. The patient had no related radiculopathy or myelopathy, and neurologic status was intact. There was severe limitation of cervical spine movements. Plain radiographs indicated age-related degenerative changes with typical features of ankylosing spondylitis with a bamboo spine appearance and gross fusion of all the vertebrae. The only mobile cervical spinal level was C6-C7. Axial magnetic resonance imaging revealed a right-sided juxtafacetal lesion at C6-C7 level that was hyperintense on T2 and hypointense on T1 imaging. A percutaneous endoscopic posterior cervical foraminotomy at right-sided C7-T1 was performed under general anesthesia. The cyst was removed, and adequate decompression of the C7 root was achieved. Postoperative magnetic resonance imaging and computed tomography scan showed adequate foraminotomy and decompression of the neural structures. The patient had gross relief of neck pain (visual analog scale score 2). CONCLUSIONS: The findings suggest that ankylosing spondylitis may cause formation of a juxtafacetal cyst at the mobile levels in a relatively less mobile cervical spine. The endoscopic resection of such cysts is a minimally invasive novel procedure that can cure such patients successfully without unwanted fusion surgery.

Anatomical Relationship of the Vertebral Artery With the Lateral Recess: Clinical Importance for Posterior Cervical Foraminotomy.

OBJECTIVE: Vertebral artery injuries during posterior cervical foraminotomy are rare, but can be fatal. Therefore, we investigated the anatomical correlation between the lateral recess and the vertebral artery. METHODS: On axial cuts of cervical magnetic resonance imaging from 108 patients, we measured the distance between the vertebral arteries and the medial border of the facet joints. The anatomical vertebro-facet distance (AVFD), surgical vertebro-facet distance (SVFD), and vertebro-facet angle (VFA) were measured. RESULTS: The mean AVFD values on the right side at the C3-4, C4-5, C5-6, and C6-7 levels showed statistically significant differences. On the right side, the mean SVFD values were equivalent to the AVFD values. The mean values of the VFA on the right side at all levels showed statistically significant differences. For all measurements, the greatest differences were seen between the C5-6 and C6-7 levels, and higher levels were associated with smaller distances from the lateral recess. The mean values of the AVFD on the right and left sides showed statistically significant differences at all levels, and the distances on the left were smaller than those on the right. CONCLUSION: The vertebral artery is closer to the lateral recess at higher cervical levels than at lower cervical levels. The largest distances were found at the C5-6 and C6-7 levels, and the left vertebral arteries were closer to the lateral recess than the right vertebral arteries.

X-rays and scans can fail to differentiate hip pathology from lumbar spinal stenosis: Two case reports.

BACKGROUND: Occasionally, hip pathologies may present alone or combined with lumbar spine pathology, especially lumbar stenosis. Although the history and clinical examination may help differentiate between the two, hip X-rays alone without accompanying magnetic resonance imaging (MRI) studies may prove unreliable. CASE DESCRIPTIONS: Case 1 - A 72-year-old male presented with the sudden onset of severe back and left posterior thigh pain. Straight leg raising test was positive at 70° (right) and 60° (left), and he had left lower extremity numbness and weakness. The lumbar MRI showed L5-S1 spinal stenosis. Although X-rays of both hips were negative, the MRI showed bilateral femoral neck fractures. He underwent screw fixation of the hip fractures and later underwent endoscopic decompression of the spinal stenosis. Case 2 - A 35-year-old male presented with low backache and right hip pain of 1 month's duration. The neurological examination was normal, except for positive straight leg raising bilaterally at 60°. The spine MRI was normal. However, despite negative X-ray of both hips, the hip MRI revealed avascular necrosis (AVN) of both femoral heads requiring subsequent orthopedic management. CONCLUSION: Hip pathology may mimic lumbar spinal stenosis. In the two cases presented, plain X-rays failed to document hip fractures (case 1) and AVN (case 2), respectively, both of which were later diagnosed on MRI studies.

Symptomatic Tuberculous Ligamentum Flavum Cyst Treated by Full Endoscopic Resection: Review with Technical Notes.

BACKGROUND: Tuberculosis (TB) of the posterior spinal element is an uncommon condition. In a developed country its diagnosis is becoming difficult due to low incidence. CASE DESCRIPTION: A 60-year-old lady presented with low back pain and right leg pain for 6 months. On examination there was tenderness over L4 and L5, a positive straight leg raise test at 70 degrees on the right side and free on the left, and sensory involvement on the right L5 dermatome. Initial magnetic resonance imaging (MRI) showed an L4-5 ligamentum flavum cyst, high signal intensity in the right pedicle and facet joint. It was considered to be a degenerative spinal disorder. Later MRI showed increased size of the cyst, and computed tomography revealed erosion of the right pedicle of the L5 vertebrae, which raised the suspicion of the tubercular pathology. Initially the patient was managed for a degenerative spinal disorder. Later, when tubercular pathology was suspected, she underwent full endoscopic uniportal stenosis decompression and excision biopsy of the cyst. The histology of the cyst revealed chronic granulomatous inflammation with central necrosis. The diagnosis of a TB cyst was confirmed, and antitubercular therapy was started. CONCLUSION: TB of the posterior elements of the spine is a diagnostic challenge in developed parts of the world. We describe the first likely case of tubercular ligamentum flavum cyst, which was managed by a full endoscopic uniportal approach.

Percutaneous Transforaminal Endoscopic Radiofrequency Ablation of the Sinuvertebral Nerve in an Olympian with a Left L5 Pedicle/Pars Interarticularis Fracture-Associated Left L5-S1 Disk Desiccation.

BACKGROUND: Irritation of the sinuvertebral nerve by a posterior or posterolateral disk desiccation can cause somatic referred pain that can mimic a lumbar radiculopathy. We present a case of a patient presenting with this condition and the positive result in pain improvement after endoscopic radiofrequency ablation of the sinuvertebral nerve. CASE DESCRIPTION: An 18-year-old Olympic runner presented to our clinic with back pain and left leg pain in a clear L5 distribution. He did not have a history of trauma. His imaging did not demonstrate any lesion causing compression of the left L5 nerve root as expected. He was found to have a left healing L5 pedicle fracture and ipsilateral chronic L5 pars interarticularis fracture. He was also found to have an ipsilateral minor left L5-S1 disk desiccation. His visual analog scale (VAS) score was 7. After a positive provocative diskogram, the patient underwent percutaneous transforaminal endoscopic radiofrequency ablation of the left L5 sinuvertebral nerve, which was irritated by the left L5-S1 disk desiccation. At his 6-month follow-up visit, the patient's VAS score was 1. CONCLUSIONS: It is important for clinicians to remember that back-associated leg pain can be caused by somatic referred pain because of irritation of the sinuvertebral nerve. Endoscopic radiofrequency of this nerve can be beneficial in pain control, but further randomized prospective trials are needed to study these techniques further.

Evolution of Spinal Endoscopic Surgery.

Innovations in the development of endoscopic spinal surgery were classified into different generations and reviewed. Future developments and directions for endoscopic spinal surgery were discussed. Surgical therapy for spinal disease has been gradually changing from traditional open surgery to minimally invasive spinal surgery. Recently, endoscopic spinal surgery, which initially was limited to the treatment of soft tissue lesions, has expanded to include other aspects of spinal disease and good clinical results have been reported. As the paradigm of spinal surgery shifts from open surgery to endoscopic surgery, we discussed the evolution of endoscopic spine surgery in our literature review. Through this description, we presented possibilities of future developments and directions in endoscopic spine surgery.

Cerebral arteriovenous malformation associated with moyamoya disease.

The coexistence of moyamoya disease (MMD) with an arteriovenous malformation (AVM) is exceedingly rare. We report two cases of AVM associated with MMD. The first case was an incidental AVM diagnosed simultaneously with MMD. This AVM was managed expectantly after encephalo-duro-arterio-synangiosis (EDAS) as the main feeders stemmed from the internal carotid artery, which we believed would be obliterated with the progression of MMD. However, the AVM persisted with replacement of the internal carotid artery feeders by new external carotid artery feeders from the EDAS site. The AVM was eventually treated with gamma knife radiosurgery considering an increasing steal effect. The second case was a de novo AVM case. The patient was initially diagnosed with MMD, and acquired an AVM eight years later that was slowly fed by the reconstituted anterior cerebral artery. Because the patient remained asymptomatic, the AVM is currently being closely followed for more than 2 years without further surgical intervention. Possible differences in the pathogenesis and the radiologic presentation of these AVMs are discussed with a literature review. No solid consensus exists on the optimal treatment of MMD-associated AVMs. Gamma knife radiosurgery appears to be an effective treatment option for an incidental AVM. However, a de novo AVM may be managed expectantly considering the possible risks of damaging established collaterals, low flow characteristics, and probably low risks of rupture.

Microsurgical treatment and outcome of pediatric supratentorial cerebral cavernous malformation.

OBJECTIVE: The purpose of this study was to investigate the clinical features and outcomes of pediatric cavernous malformation (CM) in the central nervous system. METHODS: Twenty-nine pediatric patients with supratentorial CM underwent microsurgical excision. In selected cases, transparent tubular retractor system (TTRS) was used to reduce retraction injury and intraoperative neuromonitoring (IONM) was held to preserve functioning cortex. Patients' demographics and symptoms were reviewed and surgical outcomes were discussed. RESULTS: THE MAIN INITIAL CLINICAL MANIFESTATIONS INCLUDED THE FOLLOWING : seizures (n=13, 45%), headache (n=7, 24%), focal neurological deficits (n=3, 10%), and an incidental finding (n=6, 21%). Overt hemorrhage was detected in 7 patients (24%). There were 19 children (66%) with a single CM and 10 (34%) children with multiple CMs. In 7 cases with deep-seated CM, we used a TTRS to minimize retraction. In 9 cases which location of CM was at eloquent area, IONM was taken during surgery. There was no major morbidity or mortality after surgery. In the 29 operated children, the overall long-term results were satisfactory : 25 (86%) patients had no signs or symptoms associated with CMs, 3 had controllable seizures, and 1 had mild weakness. CONCLUSION: With the assistance of neuronavigation systems, intraoperative neuromonitoring, and TTRS, CMs could be targeted more accurately and excised more safely. Based on the satisfactory seizure outcome achieved, complete microsurgical excision in children is recommended for CMs presenting with seizures but removal of hemosiderin-stained areas seems to be unnecessary.

Endoscopic Decompression for Optic Neuropathy in McCune-Albright Syndrome.

McCune-Albright syndrome (MAS) is characterized by a triad of poly/monostotic fibrous dysplasia, café-au-lait macules and hyperfunctioning endocrinopathies including human growth hormone excess. Acromegaly as a manifestation of endocrine hyperfunction with MAS is uncommon. Surgical excision may be challenging due to the associated severe fibrous dysplasia of the skull base. Through the endoscopic procedures, we treated a case of MAS presenting with compressive optic neuropathy due to fibrous dysplasia and acromegaly caused by growth hormone secreting pituitary adenoma. We reviewed the literature on GH excess in MAS to highlight its surgical and medical challenges.