Biomedical subjects

Eric L Zager

Publications and source records attributed to Eric L Zager.

At least 19 recordsLinked to original sources

PubMed2007

Neural engineering to produce in vitro nerve constructs and neurointerface.

OBJECTIVE: Recently, our laboratory recapitulated a natural form of axon growth that occurs between late embryogenesis and early adulthood. In this article, we describe how this novel neural engineering approach may be used to produce a nervous tissue interface to integrate disconnected motor and sensory functions for external control. METHODS: For nervous system repair, we recently developed a unique method to engineer nervous tissue constructs in vitro consisting of bundles of axons spanning two populations of neuronal somata. To integrate electronics and nervous tissue to transform electrophysiological signals into electronic signals, we have designed a nervous tissue interface. RESULTS: Our nervous tissue interface consists of stretch-grown nervous tissue with one end interfaced with a multiple electrode array, enabling us to detect and record real-time efferent signals conducted down the nerve and stimulate afferent sensory signaling. CONCLUSION: Our ultimate goal is to develop a neurally controlled prosthesis and a nervous system interface that could be linked to the patient's thoughts, providing two-way signaling for motor control and feedback from multiple external stimuli.

Axons↗

PubMed2006

Tumors of the peripheral nerves and plexuses.

Peripheral nerve tumors are a diverse group of lesions histologically and in their clinical behavior. The genetic disorders neurofibromatosis type 1 and 2 and schwannomatosis are significant risk factors for the development of peripheral nerve tumors. An understanding of these disorders is important in allowing appropriate management. Active treatment of peripheral nerve tumors is reserved for lesions that are malignant or causing neurologic dysfunction, pain, compressive symptomatology, or cosmetic concern. The mainstay of treatment is surgical intervention, the nature of which will vary with the type of tumor and anatomical location. In the case of malignant tumors, adjuvant chemotherapy and radiotherapy are commonly used. Developments in the understanding of the genetics and molecular biology of peripheral nerve tumors are opening up potentially exciting new avenues of treatment. The prognosis of benign peripheral nerve tumors is excellent, with a recurrence rate of just 5% or less after successful surgery. Malignant tumors have proven to be more challenging, with a much higher recurrence rate and a 5-year survival rate of 64%.

Journal Article↗

PubMed2006

Dystrophic calcification and infraclavicular brachial plexopathy: case report.

OBJECTIVE: Dystrophic calcification refers to heterotopic formation of calcium in soft tissue. There have been few reports that describe dystrophic calcification causing brachial plexopathies. We describe a unique case of dystrophic calcification that caused entrapment of the posterior cord of the brachial plexus, something not previously described in the literature. CLINICAL PRESENTATION: We report the case of a 43-year-old woman with a medical history of congenital lymphangiomas of the left chest wall and axilla, for which she had undergone multiple surgeries and radioactive seed implantation. She presented 41 years later with progressive left arm paresthesias, pain, and weakness. Neurological findings were confined to the distribution of the posterior cord of the plexus. Radiographic evaluation demonstrated a 3 x 3 x 4-cm calcified mass in the axilla and proximal arm. INTERVENTION: A careful neurolysis and mass resection was performed. At exploration, the posterior cord, proximal radial nerve, and brachial artery were found to be densely adherent to a calcified mass. Reconstruction of the brachial artery and free tissue transfer were required for healing of the severely scarred wound. Pathological examination revealed dense, calcified connective tissue consistent with dystrophic calcification. She made an excellent recovery. CONCLUSION: We describe a rare case of dystrophic calcification of the proximal arm causing symptomatic brachial plexopathy, with onset many years after surgery and radiation. Diagnostic evaluation and surgical management are discussed.

Adult↗

PubMed2006

Recurrent late cerebral necrosis with aggressive characteristics after radiosurgical treatment of an arteriovenous malformation. Case report.

/Late cerebral radiation necrosis usually occurs within 3 years of stereotactic radiosurgery. The authors report on a case of recurrent radiation necrosis with rapid clinical deterioration and imaging findings resembling those of a malignant glioma. This 68-year-old man, who had a history of a left posterior temporal and thalamic arteriovenous malformation (AVM) treated with linear accelerator radiosurgery 13 years before presentation and complicated by radiation necrosis 11 years before presentation, exhibited new-onset mixed aphasia, right hemiparesis, and right hemineglect. Imaging studies demonstrated hemorrhage and an enlarging, heterogeneously enhancing mass in the region of the previously treated AVM. The patient was treated medically with corticosteroid agents, and stabilized temporarily. Unfortunately, his condition worsened precipitously soon thereafter, requiring the placement of a shunt for relief of obstructive hydrocephalus. Further surgical intervention was offered, but the patient's family opted for hospice care instead. The patient died 10 weeks after initially presenting to the authors' institution, and the results of an autopsy demonstrated radiation necrosis. Symptomatic radiation necrosis can occur more than a decade after stereotactic radiosurgery, necessitating patient follow up during a longer period of time than currently practiced. Furthermore, there is a need for more careful reporting on the natural history of such cases to clarify the pathogenesis of very late and recurrent radiation necrosis after radiosurgery and to define patient groups with a higher risk for these entities.

Aged↗

PubMed2005

Mineral volume and morphology in carotid plaque specimens using high-resolution MRI and CT.

OBJECTIVE: High-resolution MRI methods have been used to evaluate carotid artery atherosclerotic plaque content. The purpose of this study was to assess the performance of high-resolution MRI in evaluation of the quantity and pattern of mineral deposition in carotid endarterectomy (CEA) specimens, with quantitative micro-CT as the gold standard. METHODS AND RESULTS: High-resolution MRI and CT were compared in 20 CEA specimens. Linear regression comparing mineral volumes generated from CT (VCT) and MRI (VMRI) data demonstrated good correlation using simple thresholding (VMRI=-0.01+0.98VCT; R2=0.90; threshold=4xnoise) and k-means clustering methods (VMRI=-0.005+1.38VCT; R2=0.93). Bone mineral density (BMD) and bone mineral content (BMC [mineral mass]) were calculated for CT data and BMC verified with ash weight. Patterns of mineralization like particles, granules, and sheets were more clearly depicted on CT. CONCLUSIONS: Mineral volumes generated from MRI or CT data were highly correlated. CT provided a more detailed depiction of mineralization patterns and provided BMD and BMC in addition to mineral volume. The extent of mineralization as well as the morphology may ultimately be useful in assessing plaque stability.

Adult↗

PubMed2005

Cost-effectiveness of intraoperative imaging in carotid endarterectomy.

OBJECTIVE: There has never been a large, randomized controlled trial to assess the impact of intraoperative imaging on the success of carotid endarterectomy (CEA). This comparison involves cost-effectiveness analysis. METHODS: We constructed a decision-analytic model to compare effectiveness and costs of intraoperative ultrasound (IUS) and completion angiography as adjuncts to CEA. Data on procedural mortality, morbidity, and costs were obtained from the English-language literature. The review included a total of 52 reports, encompassing more than 22,000 patients. The main components of costs were those of the monitoring interventions and the care of perioperative stroke. RESULTS: Mean perioperative outcome without completion imaging is approximately 96.7% of what it would be in the absence of perioperative stroke or death. IUS and completion angiography each result in approximately 2% improvement in expected outcome. Mean perioperative costs are 396.50 dollars for IUS, 721.30 dollars for no monitoring, and 840.90 dollars for completion angiography. Because IUS is significantly more effective at detecting technical errors that would likely result in perioperative stroke than no imaging and is significantly less costly than angiography, this strategy dominates the other two (i.e., it provides greater effectiveness at lower cost). CONCLUSION: Although surgical complications are uncommon, IUS substantially lowers the rate of perioperative stroke and mortality and thus is significantly more cost-effective than either completion angiography or no operative imaging.

Angiography↗

PubMed2005

Diagnosis and treatment options for nerve sheath tumors.

The purpose of this review is to discuss the contemporary diagnosis and treatment options for nerve sheath tumors. Common nerve sheath tumors include schwannomas, neurofibromas and malignant nerve sheath tumors. Nerve sheath tumors can be associated with genetic disorders such as neurofibromatosis and schwannomatosis. There is great variation in terms of tumor location, clinical presentation and treatment strategy. Magnetic resonance imaging is the diagnostic study of choice for nerve sheath tumors and surgery has become the mainstay of treatment for most symptomatic lesions. Progress in microsurgical techniques has resulted in significant improvement in surgical outcome, with preservation of neurologic function. Complete resection of benign nerve sheath tumors is the goal of surgical intervention and this results in cure. In contrast, malignant nerve sheath tumors remain a major challenge with poor outcomes overall. Progress in multidisciplinary research may ultimately lead to novel therapeutic strategies.

Humans↗

PubMed2005

Cervical spine meningioma presenting as otalgia: case report.

OBJECTIVE AND IMPORTANCE: Cervical spine meningiomas have not been reported to present as otalgia. It is important to include otalgia in the differential diagnosis and workup, especially when more common causes of ear pain have been excluded. CLINICAL PRESENTATION: A 66-year-old woman presented to her primary care physician with severe ear pain. She underwent routine diagnostic testing and eventually was referred to a neurologist. After conservative management failed, the patient underwent cervical spine magnetic resonance imaging, which revealed a large meningioma encompassing C2-C3. INTERVENTION: The patient underwent a cervical laminectomy with complete resection of the tumor. She experienced immediate postoperative resolution of her symptoms. CONCLUSION: This case illustrates the importance of aggressive evaluation of otalgia when routine diagnostic studies are inconclusive. Cervical meningiomas are associated with significant potential morbidity and should be excluded early in the diagnostic process.

Aged↗

PubMed2004

Pathophysiology of peripheral nerve injury: a brief review.

Clinicians caring for patients with brachial plexus and other nerve injuries must possess a clear understanding of the peripheral nervous system's response to trauma. In this article, the authors briefly review peripheral nerve injury (PNI) types, discuss the common injury classification schemes, and describe the dynamic processes of degeneration and reinnervation that characterize the PNI response.

Axons↗

PubMed2004

Case studies for illustration and discussion: peripheral nerve tumors.

This article gives a presentation of a variety of surgical cases of peripheral nerve tumors for illustration and discussion. The first three cases include a schwannoma, a neurofibroma, and a desmoid tumor of the brachial plexus region. Case 4 is that of a patient with a common peroneal ganglion cyst, and case 5 is that of a patient with an angiolipoma of the forearm. Cases 6 through 8 illustrate a plexiform neurofibroma, a malignant peripheral nerve sheath tumor, and a metastatic carcinoma to the brachial plexus region. In case 9, a patient with schwannomatosis was treated for multiple spinal schwannomas.

Adult↗

PubMed2004

Surgical management of brachial plexus region tumors.

BACKGROUND: Brachial plexus region tumors are uncommon and often present a challenge to neurosurgeons. METHODS: Provide a brief historical overview, a description of the anatomy, and contribute information that provides management guidelines and improves surgical outcomes for tumors of the brachial plexus region. We also review different surgical approaches followed by surgical outcome from recent studies, as well as our own experience of treating 42 patients with tumors of the brachial plexus region at the University of Pennsylvania Medical Center between 1990 and 2001. RESULTS: A thorough understanding of the anatomy, the clinical presentation, imaging techniques, and the various surgical approaches for brachial plexus tumor resection is necessary to ensure the best possible treatment outcome. CONCLUSION: We conclude that with proper patient selection and appropriate perioperative and intraoperative management, neurologic deficits from brachial plexus tumor surgery can be minimized.

Brachial Plexus↗

PubMed2004

Management of patients with schwannomatosis: report of six cases and review of the literature.

BACKGROUND: Schwannomatosis is a rare tumor syndrome characterized by the presence of multiple schwannomas without the stigmata of neurofibromatosis (NF) Type 1 or 2. To better understand the natural history and clinical management of the syndrome, a retrospective review was conducted of patients diagnosed with schwannomatosis over an 11-year period at the University of Pennsylvania Medical Center (UPMC). METHODS: Between 1990 and 2001, 131 patients underwent surgery for resection of spinal or peripheral nerve schwannomas in the Department of Neurosurgery at the University of Pennsylvania Medical Center. Among the 131 patients, there were 6 who had two or more pathologically proven schwannomas without radiographic or clinical evidence of vestibular schwannomas. The hospital charts, clinic notes, radiology films, operative reports, pathology slides, and reports from all 6 patients were retrospectively reviewed. RESULTS: The patient population consisted of 6 patients with a mean age of 48.7 (3 male: 3 female). All patients had enhanced brain magnetic resonance imaging (MRI) scans that were negative for vestibular schwannomas. Ophthalmological and general physical examinations did not reveal any findings suggestive of NF. There was no family history of NF or schwannomatosis. The locations of the schwannomas included intraspinal (multiple sites), paraspinal, brachial plexus, femoral nerve, sciatic nerve, calf, forearm, retroperitoneum, and middle cranial/infratemporal fossa region. The common presenting symptoms included paresthesias, palpable mass, pain, or weakness. All 6 patients underwent surgical resection of symptomatic lesions. CONCLUSIONS: For patients with schwannomatosis, surgery is indicated for symptomatic lesions, while asymptomatic tumors are followed conservatively. Because these patients are at increased risk for developing multiple schwannomas, we recommend regular surveillance and offer genetic counseling even though the pattern of inheritance is unknown.

Adolescent↗

PubMed2004

Rapid cognitive decline following lumbar puncture in a patient with a dural arteriovenous fistula.

BACKGROUND: Dural arteriovenous fistulas (DAVFs) are frequently accompanied with raised intracranial pressure and clinical findings suggestive of pseudotumor cerebri. However, unlike pseudotumor cerebri, the clinical response to lumbar cerebrospinal fluid (CSF) removal can vary from beneficial to acute clinical deterioration leading to death. The criteria for the safe use of lumbar puncture (LP) in patients with a DAVF are not well established. METHODS: A 61-year-old man presented with visual difficulty. Magnetic resonance imaging (MRI) and angiography revealed a left transverse sinus DAVF. He underwent multiple embolizations of arterial feeders over 3 years. He was then noted to have cognitive deficits in short term memory, listening, and concentrating. Over several days after an LP he became increasingly lethargic but arousable. Within hours after a repeat LP there was a rapid deterioration in the patient's level of consciousness and he became unarousable. RESULTS: A brain MRI revealed extensive dilated cortical veins and left temporal lobe venous ischemia without tonsillar herniation. A cerebral angiogram showed an extensive left transverse sinus DAVF with an occluded lateral transverse sinus and increased retrograde venous drainage. Embolization of the arterial feeders in combination with trans-venous coil embolization of the left transverse sinus reversed the patient's neurologic decline. He was discharged neurologically intact except for his chronic visual acuity problems. CONCLUSION: We speculate that when a DAVF manifests retrograde venous flow sufficient to cause cognitive deficits, lumbar CSF drainage must be undertaken with extreme caution.

Central Nervous System Vascular Malformations↗

PubMed2004

Mini-open carpal tunnel decompression.

Carpal tunnel syndrome is the most common entrapment neuropathy, and it is caused by compression of the median nerve at the wrist. The authors describe the mini-open carpal tunnel technique for surgical release of the transverse carpal ligament. The success of the procedure depends on meticulous technique with attention to certain important anatomic details and careful avoidance of injury to the palmar cutaneous nerve and the recurrent motor branch.

Carpal Tunnel Syndrome↗

PubMed2004

Thoracic outlet syndrome.

OBJECTIVE: Thoracic outlet syndrome (TOS) is one of the most controversial clinical entities in medicine. We provide a review of this difficult-to-treat disorder, including a brief overview, clinical presentations, surgical anatomy, treatment options, and outcomes. METHODS: TOS represents a spectrum of disorders encompassing three related syndromes: compression of the brachial plexus (neurogenic TOS), compression of the subclavian artery or vein (vascular TOS), and the nonspecific or disputed type of TOS. Neurovascular compression may be observed most commonly in the interscalene triangle, but it also has been described in the costoclavicular space and in the subcoracoid space. Patients present with symptoms and signs of arterial insufficiency, venous obstruction, painless wasting of intrinsic hand muscles, paresthesia, and pain. A careful and detailed medical history and physical examination are the most important diagnostic tools for proper identification of TOS. Electromyography, nerve conduction studies, and imaging of the cervical spine and the chest also can provide helpful information regarding diagnosis. Clinical management usually starts with conservative treatment including exercise programs and physical therapy; when these therapies fail, patients are considered for surgery. Two of the most commonly used surgical approaches are the supraclavicular exposure and the transaxillary approach with first rib resection. On occasion, these approaches may be combined or, alternatively, posterior subscapular exposure may be used in selected patients. CONCLUSION: TOS is perhaps the most difficult entrapment neuropathy encountered by neurosurgeons. Surgical intervention is indicated for vascular and true neurogenic TOS and for some patients with the common or nonspecific type of TOS in whom nonoperative therapies fail. With careful patient selection, operative intervention usually yields satisfactory results.

Humans↗

PubMed2004

Ulnar nerve entrapment neuropathy at the elbow: simple decompression.

Ulnar nerve entrapment neuropathy at the elbow, or the cubital tunnel syndrome, is frequently encountered in neurosurgical practice as the second most common peripheral nerve entrapment after carpal tunnel syndrome. Patients typically present with weakness or atrophy of the hand as well as paresthesias in the ulnar nerve distribution. The diagnosis can be confirmed with a careful clinical examination and electrophysiological studies. Patients who have failed conservative therapy are considered for surgery. Although a number of surgical options are available, simple decompression of the ulnar nerve can achieve satisfactory results with appropriate patient selection. We describe the relevant anatomy and surgical techniques for simple in situ decompression of the ulnar nerve at the elbow.

Decompression, Surgical↗

PubMed2004

Continuous arterial spin labeled perfusion magnetic resonance imaging in patients before and after carotid endarterectomy.

Continuous arterial spin labeling perfusion magnetic resonance imaging (CASL-pMRI) uses magnetically labeled arterial blood water as a tracer to obtain quantifiable measurements of cerebral blood flow (CBF) (mL/100 g-1/min-1). CASL-pMRI was used to assess CBF changes in major vascular distributions in patients (n = 10) prior to and 3 months after carotid endarterectomy (CEA). No significant change in the global baseline CBF before and after CEA was observed in the group as a whole (P = .81). In patients with reduced CBF prior to CEA (< 50 ml/100 g/min), a significant increase in global CBF following CEA was observed. An inverse relationship existed between percent change in CBF after CEA versus baseline CBF within the anterior circulation (r = -.78, P < .05) but not in the posterior distribution (r = .25, P = .63). CASL-pMRI may provide a convenient, inexpensive, noninvasive method for identifying CEA patients at risk for hyperperfusion following carotid revascularization.

Aged↗

PubMed2003

Intradural venous varix: a rare cause of an intradural lumbar spine lesion.

STUDY DESIGN: A case of intradural venous varix producing a mass-like lesion in the lumbar spine is reported. OBJECTIVE: To present a rare cause of an intradural mass lesion along the cauda equina. To present radiologic findings of this entity and to offer a hypothesis for its formation. SUMMARY OF BACKGROUND DATA: Epidural venous varices have been described previously in the literature. To the authors' knowledge, no cases of intradural venous varix presenting as an intradural mass have been reported previously. MATERIALS AND METHODS: An elongated, serpentine intradural mass was discovered on routine lumbar MRI performed for investigation of the patient's radiculopathy. The patient underwent laminectomy and intradural exploration. RESULT: On surgical exploration, a serpentine, massively dilated vein was identified, which distorted the normal nerve roots. CONCLUSION: A venous varix should be considered in the differential diagnosis of an intradural lesion in the lumbar spine in the appropriate clinical setting.

Aged↗