Kostas N. Fountas

Anterior Cervical Discectomy and Fusion Associated Complications

Study Design. Retrospective review study with literature review. Objective. The goal of our current study is to raise awareness on complications associated with anterior cervical discectomy and fusion (ACDF) and their early detection and proper management. Summary of Background Data. It is known that ACDF constitutes one of the most commonly performed spinal procedures. Its outcome is quite satisfactory in the majority of cases. However, occasional complications can become troublesome, and in rare circumstances, catastrophic. Although there are several case reports describing such complications, their rate of occurrence is generally underreported, and data regarding their exact incidence in large clinical series are lacking. Meticulous knowledge of potential intraoperative and postoperative ACDF-related complications is of paramount importance so as to avoid them whenever possible, as well as to successfully and safely manage them when they are inevitable. Methods. In a retrospective study, 1015 patients undergoing first-time ACDF for cervical radiculopathy and/or myelopathy due to degenerative disc disease and/or cervical spondylosis were evaluated. A standard Smith-Robinson approach was used in all our patients, while an autologous or allograft was used, with or without a plate. Operative reports, hospital and outpatient clinic charts, and radiographic studies were reviewed for procedure-related complications. Mean follow-up time was 26.4 months. Results. The mortality rate in our current series was 0.1% (1 of 1015 patients, death occurred secondary to an esophageal perforation). Our overall morbidity rate was 19.3% (196 of 1015 patients). The most common complication was the development of isolated postoperative dysphagia, which observed in 9.5% of our patients. Postoperative hematoma occurred in 5.6%, but required surgical intervention in only 2.4% of our cases. Symptomatic recurrent laryngeal nerve palsy occurred in 3.1% of our cases. Dural penetration occurred in 0.5%, esophageal perforation in 0.3%, worsening of preexisting myelopathy in 0.2%, Horner’s syndrome in 0.1%, instrumentation backout in 0.1%, and superficial wound infection in 0.1% of our cases. Conclusion. Meticulous knowledge of the ACDF-associated complications allows for their proper management. Postoperative dysphagia, hematoma, and recurrent laryngeal nerve palsy were the most common complications in our series. Management of complications was successful in the vast majority of our cases.

Implantation of a closed-loop stimulation in the management of medically refractory focal epilepsy : A technical note

Open-loop stimulation studies have shown varying control of seizures with stimulation of different anatomical targets. A recent multi-institutional clinical study utilizing an external closed-loop stimulation system had promising results. A novel implantable closed-loop Responsive Neurostimulation System (RNS) (Neuropace, Inc., Mountainview, Calif., USA) consisting of a cranially implanted pulse generator, one or two quadripolar subdural strip or depth leads and a programmer is under testing in a prospective clinical trial. The RNS pulse generator continuously analyzes the patient’s electrocortigrams (ECoGs) and automatically triggers electrical stimulation when specific ECoG characteristics programmed by the clinician, as indicative of electrographic seizures or precursor of epileptiform activities, are detected. The pulse generator then stores diagnostic information detailing detections and stimulations, including multichannel stored ECoGs. The RNS programmer communicates transcutaneously with the implanted pulse generator when initiated by a clinician. The RNS programmer can download diagnostics and store ECoGs for review. The RNS programmer can then be used to program detection and stimulation parameters. In our current communication, we describe the selection criteria for implanting this system, the preparation of the surgical candidates as well as the surgical technique. We also present our preliminary results with 8 patients who had an RNS implanted. Seven patients (87.5%) had more than 45% decrease in their seizure frequency. The mean follow-up time in our series was 9.2 months. The implantation of a closed-loop stimulation system, in our experience, represents a safe and relatively simple surgical procedure. However, the efficacy of this new treatment modality remains to be determined in further multi-institutional, prospective clinical studies.

Management of intracranial meningeal hemangiopericytomas: outcome and experience

Hemangiopericytomas represent rare intracranial tumors that have a tendency to recur locally and have the unique characteristic of giving extracranial metastases. Our current communication reviews a series of patients diagnosed with hemangiopericytoma who were treated in our facility. Eleven patients with a mean age of 51.2 years underwent follow-up for a mean time of 7.1 years. Their neuroimaging preoperative evaluation included plain skull X-rays, head CT scans, brain MRI, angiograms, and 1HMRS. Preoperative embolization of the tumor was employed in 6/11 patients. All patients underwent craniotomy for tumor resection and postoperative radiation treatment was employed on all but one. Grade I resection was accomplished in 6/11 (54.5%), grade III in 4/11 (36.4%), and grade IV in 1/11 (9.1%). Local recurrence was detected in 3/11 (27.3%) at a mean period of 5 (range 2–7.5) years. Extracranial metastatic disease was documented in 4/11 (36.4%) patients at a mean of 4.9 (range 2.5–7) years after the initial diagnosis. The GOS score was: 7/11 (63.6%) scored 5, while 4/11 (36.4%) died at a mean time of 5.5 (range 3–8) years after the initial diagnosis. Intracranial hemangiopericytomas management requires aggressive surgical resection, postoperative radiation treatment, and extensive follow-up to rule out local recurrences and delayed extracranial metastases.

Cerebral venous sinus thrombosis: review of the demographics, pathophysiology, current diagnosis, and treatment

Cerebral venous sinus thrombosis (CVST) is a rare clinicopathological entity. The incidence of CVST in children and neonates has been reported to be as high as 7 cases per million people, whereas in adults the incidence is 3-4 cases per million. The predisposing factors to this condition are mainly genetic and acquired prothrombotic states and infection. The clinical picture of CVST is nonspecific, highly variable, and can mimic several other clinical conditions. Diagnosis of CVST is established with the implementation of neuroimaging studies, especially MR imaging and venography. Identification and elimination of the underlying cause, anticoagulation, proper management of intracranial hypertension, and anticonvulsant prophylaxis constitute cornerstones of CVST treatment. Newer treatment strategies such as endovascular thrombolysis and decompressive craniectomy have been recently used in the treatment of patients with CVST with variable success rates. Further clinical research must be performed to delineate the exact role of these newer treatments in the management of severe cases of CVST. The recent advances in the diagnosis and treatment of patients with CVST have significantly lowered the associated mortality and morbidity and have improved the outcome of these patients.

Subdural Electrode-Associated Complications: A 20-Year Experience

Background: Implantation of subdural strip and grid electrodes is a common methodology in the invasive evaluation of patients with medically refractory epilepsy. Although their implantation is safe, the occurrence of implantation-associated complications can occasionally be troublesome. Methods: In our current retrospective study, 185 patients undergoing subdural grid/strip implantation for invasive monitoring were examined. Their ages ranged between 16 and 48 years (mean 23.6). AdTech (Racine, Wisc., USA) strip and grid electrodes were implanted under general endotracheal anesthesia in all our cases. Duration of electroencephalographic monitoring ranged from 2 to 25 days (mean 10.8). The follow-up period ranged from 24 to 60 months (mean 44.6 months). Results: The most common complication in our series was the development of postoperative epidural hematoma in 3 patients (1.6%), while 2 patients (1.1%) suffered a subdural hematoma. Two patients (1.1%) developed significant brain edema postoperatively, 2 others (1.1%) developed an infection, while 2 patients (1.1%) experienced transient aphasia. Two patients (1.1%) had fatal outcomes in our series. Interestingly, in 5 patients (2.7%) nonhabitual seizures were recorded. Conclusion: Thorough understanding, early identification and prompt management of potential complications can minimize the risks associated with the implantation of subdural electrodes.

Results of long-term follow-up in patients undergoing anterior screw fixation for type II and rostral type III odontoid fractures.

Study Design. Retrospective analysis of the fusion rate of a group of 38 patients having undergone anterior screw fixation for type II and “shallow” type III odontoid fractures. Objective. To determine primarily the long-term fusion rate after anterior screw fixation and to study the clinical characteristics of patients that have a statistically significant or nonsignificant influence on successful outcome. Summary of Background Data. Long-term outcome of anterior screw fixation for odontoid fractures has been evaluated in very few studies. This information should be critical for further establishing this technique as a major therapeutic strategy for these cases. Methods. Thirty-eight patients, 25 males and 13 females (with mean age 48.4 ± 0.4 years), with type II and rostral type III odontoid fractures, underwent anterior cannulated screw fixation during a 62-month period. Radiologic examination of the cervical spine with plain radiographs was performed at 6 weeks, and 2, 6, 12, and 24 months, while computerized tomography of the upper cervical spine (C1–C3) was obtained at 6 months after surgery. Follow-up was available for 31 patients, and the follow-up time ranged from 39 to 87 months (mean 58.4). Results. Radiographic evaluation of the follow-up group showed satisfactory bony fusion and no evidence of abnormal movement at the fracture site in 27 (87.1%) patients. Pseudarthrosis developed in 4 (12.9%) patients; however, 3 (9.6%) of them without instability and 1 (3.2%) with instability. One (3.2%) patient had an instrumentation failure without instability. Conclusions. In our series, anterior odontoid screw fixation comprised a safe therapeutic modality with high stability and low mechanical failure rates during short-term and long-term follow-up.

A novel closed-loop stimulation system in the control of focal, medically refractory epilepsy

The concept of seizure abortion after prompt detection by employing stimulation is a very appealing one. Several investigators in previous experimental and clinical studies have used stimulation of various anatomical targets with promising results. In this chapter, the authors present their experience with a novel, implantable, local closed-loop responsive neuro-stimulation system (RNS) (Neuropace, Inc., Mountain View, CA, USA). This system consists of a cranially implanted pulse generator, one or two quadripolar subdural strip or depth leads and an external programmer. The system components and technical characteristics are presented. The criteria for selecting candidates for implantation as well as the preliminary results of a clinical trial are also presented. Closed-loop stimulation system appears to be a safe treatment option with promising results for the management of patients with well-localized, focal medically-refractory epilepsy, who are not candidates for surgical resection.

Noninvasive Histologic Grading of Solid Astrocytomas Using Proton Magnetic Resonance Spectroscopy

Background: Proton magnetic resonance spectroscopy (1H MRS) constitutes a promising modality to assess intracranial pathology. We present our experience using this method in grading solid brain astrocytomas. Material and Methods: Using a 1.5-Tesla MRI unit, 71 patients with the radiographic diagnosis of astrocytoma were examined. Water-suppressed single-voxel 1H MRS was employed in all of our patients. The concentrations of choline (Cho), N-acetyl-aspartate (NAA), phosphocreatine-creatine (Pcr-Cr), myo-inositol (MI), lactate (Lac), lipids (Lip) as well as the metabolite ratios of Cho/Pcr-Cr, NAA/PCr-Cr and NAA/Cho were calculated. An appropriate surgical biopsy was performed. Standard pathology examination was employed in a double-blinded fashion. Results: An increased concentration of Cho and decreased concentrations of Pcr-Cr and NAA were detected. The concentrations of Lac, Lip and MI varied inconsistently, even among tumors of the same histologic grade. The Cho/Pcr-Cr ratio was calculated. This ratio was found to be 2.15 ± 0.26 in 27 patients with astrocytomas grade I and II, 2.78 ± 0.09 in 18 patients with grade III, and 5.40 ± 0.16 in 26 patients with grade IV. Discussion: The increased concentration of Cho is due to the increased cellularity and a relatively increased number of membranous structures in highly malignant tumors. In abnormal anaerobic metabolic tumor states there is relatively less phosphorylization of creatine. By using the Cho/Pcr-Cr ratio the concomitant effects of structural and metabolic alteration can thereby be emphasized for diagnostic advantage. Conclusion: The Cho/Pcr-Cr is a very important and statistically significant marker (p = 0.043) determining the degree of intracranial astrocytoma malignancy.

In vivo Proton Magnetic Resonance Spectroscopy of Brain Tumors

The ability of magnetic resonance spectroscopy (MRS) to differentiate neoplastic brain cells and their metabolic and structural characteristics is evaluated. We examined 120 patients with brain tumors using a 1.5-tesla MRI unit and MRS. The peak areas of N-acetyl-aspartate (NAA), phosphocreatine-creatine (Pcr-Cr), choline-containing compounds (Cho), lactate, lipids, myoinositol, amino acids and the ratios of NAA/Pcr-Cr, NAA/Cho and Cho/Pcr-Cr were calculated by a standard integral algorithm. In normal brain tissue, the following metabolites were identified: NAA at 2.0 ppm, Pcr-Cr at 3.0 ppm and Cho at 3.2 ppm. The different concentrations of the metabolites examined and their role in the biochemical profile of different types of tumors are discussed. The confidence interval of the MRS versus pathology was between 0.9 and 0.954, while it was between 0.52 and 0.631 for MRI versus pathology. The Cho/Pcr-Cr ratio is a very important malignancy marker for histologic tumor grading of astrocytomas. The greater this ratio, the higher the grade of the astrocytoma. NAA/Pcr-Cr together with Cho/Pcr-Cr help specify the presence or absence of a neoplasm. Proton MRS is a useful and promising diagnostic modality not only in diagnosing but also in grading solid brain tumors.

Outcome of Patients Undergoing Gamma Knife Stereotactic Radiosurgery for Medically Refractory Idiopathic Trigeminal Neuralgia: Medical College of Georgia’s Experience

Gamma knife radiosurgery represents an established treatment option for the management of medically refractory trigeminal neuralgia (TN). In our current communication we present our experience in radiosurgically treating patients with idiopathic TN. Over a period of 5 years, 77 patients underwent gamma knife radiosurgery. The patients were divided into 2 groups based on their previous surgical treatment. In the group of patients with no previous surgeries, the initial response rate was 92.4% (48/52 patients), while in the group with previous surgeries it was 84% (21/25 patients). The excellent outcome rates (complete pain relief with no pain medications) at the completion of 1, 2 and 3 years after treatment for the group with no previous surgeries were: 80.8% (42/52 patients), 69.2% (36/52 patients) and 53.8% (28/52 patients), respectively. The respective excellent outcome rates for the group of patients with previous surgeries were: 64% (16/25 patients), 44% (11/25 patients) and 12% (3/25 patients). The good outcome rates at the completion of 1, 2 and 3 years after treatment for the group with no previous surgeries were: 7.7% (4/52 patients), 11.5% (6/52 patients) and 19.2% (10/52 patients). The respective percentages of good outcome for the patients with previous surgery were: 12% (3/25 patients) at 1 year, 16% (4/25 patients) at 2 years and 32% (8/25 patients) at the completion of 3 years after treatment. The most commonly encountered complication in our series was the development of facial numbness. Our findings confirm previous reports that the presence of preceding surgical interventions represents a negative long-term outcome factor. However, gamma knife radiosurgery constitutes a safe and efficient minimally invasive treatment option for patients with idiopathic TN.