Frode Kolstad

Intra-operative 3D ultrasound in neurosurgery

SummaryIn recent years there has been a considerable improvement in the quality of ultrasound (US) imaging. The integration of 3D US with neuronavigation technology has created an efficient and inexpensive tool for intra-operative imaging in neurosurgery. In this review we present the technological background and an overview of the wide range of different applications. The technology has so far mostly been applied to improve surgery of tumours in brain tissue, but it has also been found to be useful in other procedures such as operations for cavernous haemangiomas, skull base tumours, syringomyelia, medulla tumours, aneurysms, AVMs and endoscopy guidance.

Transforaminal steroid injections in the treatment of cervical radiculopathy. A prospective outcome study

SummaryBackground. The aim of this study was to assess if transforaminal steroid injections applied to cohort of patients waiting for cervical disc surgery, reduce the pain of cervical radiculopathy and hence reduce the need for surgical intervention.Cervical radiculopathy due to cervical disc herniation or spondylosis is a common indication for cervical disc surgery. Surgery is however not always successful, and is not done without risk of complications.Transforaminal injection of steroids has gained popularity due to the rationale that inflammation of the spinal nerve roots causes radicular pain, and therefore steroids placed locally should relieve symptoms.Methods. During a 12-month period, 21 secondary referral patients with unilateral cervical radiculopathy entered the study. Cervical disc herniation or spondylosis affecting the corresponding nerve root was demonstrated by appropriate investigation (MRI or myelography).The patients then received 2 transforaminal steroid injections, at 2 weeks interval, while waiting for operative treatment.The pain intensity (VAS), Odom’s criteria and operative indications were registered at 6 weeks and 4 months.Findings. After receiving injection treatment 5 of the 21 patients decided to cancel the operation due to clinical improvement. A statistically significant reduction (0.02) in radicular pain score was simultaneously measured. This corresponds well with the reduction in operative requirements since radicular pain is the main indication for operative treatment. The responders experienced a long-lasting effect.Those responding positively however improved neck pain to the same extent as radicular pain, and patients with cervical spondylosis responded as positively as those with disc herniation.Interpetation. This prospective cohort study indicates a reduction in the need for operative treatment due to injection treatment. The clinical effect is measurable, and a statistically significant improvement of the radicular pain is registered.Routine transforaminal injection treatment prior to surgery seems rewarding, but the complication risk must be taken into consideration.

Long-term outcome after resection of intraspinal ependymomas: report of 86 consecutive cases.

BACKGROUND: Objective: To evaluate progression-free survival, overall survival (OS) and long-term clinical outcome in a consecutive series of 86 patients with intraspinal ependymomas. METHODS: Medical charts were retrospectively reviewed. Surviving patients voluntarily participated in a clinical history and physical examination that focused on neurological function and current tumor status. RESULTS: Follow-up data are nearly 100% complete; mean follow-up time was 82 months. Eighty-five patients (99%) had surgery as a first-line treatment; 14 (17%) of these patients received adjuvant radiotherapy. Of the 85 patients who underwent primary surgery, gross total resection was performed in 60 patients (71%) and subtotal resection in 25 patients (29%). Ten-year progression-free survival rate was 75%; 5-year OS, 97%; and 10-year OS, 91%. Reduced preoperative neurological function and older age at diagnosis were significantly associated with increased risk of death. At follow-up, spontaneous regression of residual tumor after primary surgery may have occurred in 7 of 19 patients (37%). More than 75% of patients had neurological function compatible with an independent life at follow-up. Good preoperative neurological function was significantly associated with favorable outcome. It was not possible to evaluate the effect of radiotherapy on progression-free survival and OS. CONCLUSION: Gross total resection remains the optimal treatment for patients with spinal ependymoma. Patients should be monitored with a clinical examination and magnetic resonance imaging at regular intervals up to 10 years after surgery.

Segmental motion adjacent to anterior cervical arthrodesis: a prospective study.

Study Design. Prospective, observational study. Objective. The present study describes in a prospective setting the kinematics changes occurring at segments adjacent to a one-level cervical arthrodesis. Summary of Background Data. The development of adjacent segment disease has been noticed by many clinicians. Whether symptoms develop due to fusion induced accelerated spondylosis or due to a natural development in a predisposed person is currently under debate. The motivation for introducing motion preservation procedures in the neck is primarily to protect the patients from developing symptomatic adjacent disc disease. To accept this rationale, it has to be demonstrated that a fusion creates an unfavorable biomechanical situation at adjacent levels. Methods. Forty-six patients underwent standard anterior cervical decompression and fusion using a cylindrical cage implant. Lateral radiographic views of the cervical spine in flexion and extension were obtained before surgery, and at 12 months of follow-up. Employing Distortion Compensated Roentgen Analysis, rotational and translational motion at adjacent levels was quantified prospectively. Results. Rotational and translational motion at adjacent cranial and caudal levels did not exhibit a significant change between the preoperative state and the state 12 months after the operation. Conclusion. The assumption of an iatrogenically caused increased mobility by a one-level cervical fusion could not be confirmed 12 months after surgery.

Anterior Cervical Arthrodesis Using a "Stand Alone" Cylindrical Titanium Cage : Prospective Analysis of Radiographic Parameters

Study Design. Prospective, observational study. Objective. To evaluate biomechanical changes associated with cervical arthrodesis using a cylindrical titanium cage. Summary of Background Data. Anterior cervical discectomy and fusion (ACDF) is the “gold standard” for treating cervical disc disease. In an effort to avoid the morbidity associated with autogenous bone graft harvesting, cervical cages are used to achieve fusion. The cages should allow for restoration and maintenance of natural disc height, angulations, and displacements at the operated levels. Methods. Fifty-four patients underwent standard ACDF using a “stand alone” cylindrical cage implant. Lateral radiographic views of the cervical spine were obtained before surgery, on the first day postoperatively, and at 12 months postoperatively. Disc height, vertebral alignment, angle of lordosis, and range of motion at operated levels were quantified prospectively by distortion compensated Roentgen analysis. Results. At 12 months postoperatively, solid fusion was achieved but the cylindrical cage failed to preserve disc height, prevent kyphosis, and preserve natural intervertebral alignment. We observed significant cage subsidence and malalignment. Conclusion. We noticed several unfavorable outcomes when performing an analysis of radiographic parameters after ACDF using a cylindrical titanium cage. Thus, the use of a “stand alone” cylindrical cage in ACDF should be considered with caution.

Surgical mortality and complications leading to reoperation in 318 consecutive posterior decompressions for cervical spondylotic myelopathy.

Halvorsen CM, Lied B, Harr ME, Rønning P, Sundseth J, Kolstad F, Helseth E. Surgical mortality and complications leading to reoperation in 318 consecutive posterior decompressions for cervical spondylotic myelopathy.
Acta Neurol Scand: 2011: 123: 358–365.
© 2010 John Wiley & Sons A/S.

Idiopathic Ventral Spinal Cord Herniation: An Increasingly Recognized Cause of Thoracic Myelopathy

Idiopathic spinal cord herniation (ISCH), where a segment of the spinal cord has herniated through a ventral defect in the dura, is a rarely encountered cause of thoracic myelopathy. The purpose of our study was to increase the clinical awareness of this condition by presenting our experience with seven consecutive cases treated in our department since 2005. All the patients developed pronounced spastic paraparesis or Brown-Séquard syndrome for several years (mean, 4.7 years) prior to diagnosis. MRI was consistent with a transdural spinal cord herniation in the mid-thoracic region in all the cases. The patients underwent surgical reduction of the herniated spinal cord and closure of the dural defect using an artificial dural patch. At follow-up, three patients experienced considerable clinical improvement, one had slight improvement, one had transient improvement, and two were unchanged. Two of the four patients with sphincter dysfunction regained sphincter control. MRI showed realignment of the spinal cord in all the patients. ISCH is probably a more common cause of thoracic myelopathy than previously recognized. The patients usually develop progressive myelopathy for several years before the correct diagnosis is made. Early diagnosis is important in order to treat the patients before the myelopathy has become advanced.

The Long-term Outcome After Resection of Intraspinal Nerve Sheath Tumors: Report of 131 Consecutive Cases.

BACKGROUND The existing literature on recurrence rates and long-term clinical outcome after resection of intraspinal nerve sheath tumors is limited. OBJECTIVE To evaluate progression-free survival, overall survival, and long-term clinical outcome in a consecutive series of 131 patients with symptomatic intraspinal nerve sheath tumors. METHODS Medical charts were retrospectively reviewed. Surviving patients voluntarily participated in a clinical history and physical examination that focused on neurological function and current tumor status. RESULTS Follow-up data are 100% complete; median follow-up time was 6.1 years. All patients (100%) had surgery as the first line of treatment; gross total resection was performed in 112 patients (85.5%) and subtotal resection in 19 patients (14.5%). Five-year progression-free survival was 89%. The following risk factors for recurrence were identified: neurofibroma, malignant peripheral nerve sheath tumor, subtotal resection, neurofibromatoses/schwannomatosis, and advancing age at diagnosis. More than 95% of patients had neurological function compatible with an independent life at follow-up. The rate of tumor recurrence in nonneurofibromatosis patients undergoing total resection of a single schwannoma was 3% (3/93), in comparison with a recurrence rate of 32% (12/38) in the remaining patients. CONCLUSION Gross total resection is the gold standard treatment for patients with intraspinal nerve sheath tumors. In a time of limited health care resources, we recommend that follow-up be focused on the subgroup of patients with a high risk of recurrence. The benefit of long-term, yearly magnetic resonance imaging follow-up with respect to recurrence in nonneurofibromatosis patients undergoing gross total resection of a single schwannoma is, in our opinion, questionable. 1NF2, neurofibromatosis 2NST, nerve sheath tumorOS, overall survivalPFS, progression-free survivalSTR, subtotal resectionWHO, World Health Organization.

Magnetic resonance imaging evaluation after implantation of a titanium cervical disc prosthesis: a comparison of 1.5 and 3 Tesla magnet strength.

PurposeCervical disc prostheses induce significant amount of artifact in magnetic resonance imaging which may complicate radiologic follow-up after surgery. The purpose of this study was to investigate as to what extent the artifact, induced by the frequently used Discover® cervical disc prosthesis, impedes interpretation of the MR images at operated and adjacent levels in 1.5 and 3 Tesla MR.MethodsTen subsequent patients were investigated in both 1.5 and 3 Tesla MR with standard image sequences one year following anterior cervical discectomy with arthroplasty.Outcome measuresTwo neuroradiologists evaluated the images by consensus. Emphasis was made on signal changes in medulla at all levels and visualization of root canals at operated and adjacent levels. A “blur artifact ratio” was calculated and defined as the height of the artifact on T1 sagittal images related to the operated level.ResultsThe artifacts induced in 1.5 and 3 Tesla MR were of entirely different character and evaluation of the spinal cord at operated level was impossible in both magnets. Artifacts also made the root canals difficult to assess at operated level and more pronounced in the 3 Tesla MR. At the adjacent levels however, the spinal cord and root canals were completely visualized in all patients. The “blur artifact” induced at operated level was also more pronounced in the 3 Tesla MR.ConclusionsThe artifact induced by the Discover® titanium disc prosthesis in both 1.5 and 3 Tesla MR, makes interpretation of the spinal cord impossible and visualization of the root canals difficult at operated level. Adjusting the MR sequences to produce the least amount of artifact is important.

Distinguishing Anesthetized from Awake State in Patients: A New Approach Using One Second Segments of Raw EEG

Objective: The objective of this study was to test whether properties of 1-s segments of spontaneous scalp EEG activity can be used to automatically distinguish the awake state from the anesthetized state in patients undergoing general propofol anesthesia. Methods: Twenty five channel EEG was recorded from 10 patients undergoing general intravenous propofol anesthesia with remifentanil during anterior cervical discectomy and fusion. From this, we extracted properties of the EEG by applying the Directed Transfer Function (DTF) directly to every 1-s segment of the raw EEG signal. The extracted properties were used to develop a data-driven classification algorithm to categorize patients as “anesthetized” or “awake” for every 1-s segment of raw EEG. Results: The properties of the EEG signal were significantly different in the awake and anesthetized states for at least 8 of the 25 channels (p < 0.05, Bonferroni corrected Wilcoxon rank-sum tests). Using these differences, our algorithms achieved classification accuracies of 95.9%. Conclusion: Properties of the DTF calculated from 1-s segments of raw EEG can be used to reliably classify whether the patients undergoing general anesthesia with propofol and remifentanil were awake or anesthetized. Significance: This method may be useful for developing automatic real-time monitors of anesthesia.