Liang-Shong Lee

Gamma knife surgery for cavernous hemangiomas in the cavernous sinus.

BACKGROUNDCavernous hemangioma in the cavernous sinus (CS) is a rare vascular tumor. Direct microsurgical approach usually results in massive hemorrhage. Radiosurgery has emerged as a treatment alternative to microsurgery. OBJECTIVETo further investigate the role of Gamma Knife surgery (GKS) in treating CS hemangiomas. METHODSThis was a retrospective analysis of 7 patients with CS hemangiomas treated by GKS between 1993 and 2008. Data from 84 CS meningiomas treated during the same period were also analyzed for comparison. The patients underwent follow-up magnetic resonance imaging at 6-month intervals. Data on clinical and imaging changes after radiosurgery were analyzed. RESULTSSix months after GKS, magnetic resonance imaging revealed an average of 72% tumor volume reduction (range, 56%–83%). After 1 year, tumor volume decreased 80% (range, 69%–90%) compared with the pre-GKS volume. Three patients had > 5 years of follow-up, which showed the tumor volume further decreased by 90% of the original size. The average tumor volume reduction was 82%. In contrast, tumor volume reduction of the 84 cavernous sinus meningiomas after GKS was only 29% (P < .001 by Mann-Whitney U test). Before treatment, 6 patients had various degrees of ophthalmoplegia. After GKS, 5 improved markedly within 6 months. Two patients who suffered from poor vision improved after radiosurgery. CONCLUSIONGKS is an effective and safe treatment modality for CS hemangiomas with long-term treatment effect. Considering the high risks involved in microsurgery, GKS may serve as the primary treatment choice for CS hemangiomas.

Protection of visual pathway in gamma knife radiosurgery for craniopharyngiomas.

Craniopharyngiomas present a major challenge to Gamma Knife radiosurgery (GKRS) due to their proximity to the optic apparatus. Based on observations of the evolving tumoral change on MRI and clinical results, an optimization of the treatment strategy and dose selection is possible. From March 1993 to September 1996, 21 patients with craniopharyngiomas were treated by GKRS. Every patient received stereotactic MRI exclusively for targeting and dose planning. The tumor and adjacent structures, including optic nerves, chiasm, and tracts were carefully identified and delineated on sagittal, coronal and axial films. The tumor volume ranged from 0.3 to 28 ml (average 9 ml). We purposefully apply multiple isocenters (average 9.1 shots) to create an isodose curve that covered the tumor optimally while sparing the optic pathway. The marginal dose prescribed was 9.5 to 16 Gy (50%). The maximal dose was 19 to 32 Gy. The maximal dose to the optic apparatus was 3.2 to 12.5 Gy. After GKRS, all patients were followed up clinically every month. MR studies were conducted every six months with the same techniques on the same scanner to investigate evolution of tumor volume and any adverse radiation effect. The follow-up period ranged from 6 to 40 months (mean: 18.4, median: 19). All patients were followed more than 6 months. Nineteen out of 21 cases (90.5%) achieved tumor control; that is, 18 tumor shrinkage (volume reduction: 15–95%) and 1 stabilized tumor growth. Among these 21 patients, 7 had improved visual acuity or visual field after GKRS, and the rest remained stable. Two patients developed mild T2 change on MRI without any endocrinological disturbance or visual impairment. Protection of the visual pathway can be secured by a sophisticated delineation on 3-dimensional stereotactic images with multiple-shot dose planning. Craniopharyngiomas with tumor volume up to 25 ml were treated safely and effectively, because the dose to the optic apparatus was kept as low as possiby this strategy. Further follow-up is needed to determine the highest tolerable dose to surrounding critical structures and the long-term outcome of tumor control.

Cervical root repair in adult rats after transection: recovery of forelimb motor function

Functional recovery was achieved in rats after repairing the transected left sixth and seventh cervical roots. Intercostal nerves were used for reanastomosis between the transected roots and the spinal cord, and acidic fibroblast growth factor with fibrin glue was applied. Experimental rats showed relevant functional recovery of gait and grooming reflexes. Electromyography demonstrated less denervation and more regeneration. Horseradish peroxidase retrograde axonal tracing disclosed a statistically significant increase of motor neuron survival, suggesting that motor neuron survival was significantly correlated with functional recovery. It is our belief that this novel treatment strategy may help patients with similar injuries in the future.

FUNCTIONAL CONNECTIVITY OF THE TRANSECTED BRACHIAL PLEXUS AFTER INTERCOSTAL NEUROTIZATION IN MONKEYS

Microsurgical reconstructions of brachial plexuses were performed on twelve monkeys by using ipsilateral intercostal nerves (T3‐9). Reinnervation in individual nerves was evaluated monthly by observations of neuromuscular and electromyographic improvements. The electromyographic studies revealed reappearance of motor unit potentials. According to a motor scale ranging from 0 to 4, the mean muscle power 6 months after operation improved to 2.75 in the deltoid muscles, 2 in the biceps muscles, 1.22 in the triceps muscles, 1.13 in the flexor carpi radialis muscles, and 1.6 in the intrinsic muscles of the hands. Retrograde transport of horseradish peroxidase (HRP) from the neuromuscular junctions of the reconstructed musculocutaneous nerves 6 months after complete brachial plexus lesion in four animals demonstrated HRP‐labeled neurons in the anterior horns, spinal ganglia and sympathetic ganglia of the thoracic spinal cords. It suggested that the regenerated afferent and efferent circuits in the thoracic cords innervating the transected brachial plexuses were able to generate the movements in the paralyzed upper limbs. However, as evidenced by the behavior patterns and the fact that retrograde‐labeled neurons were all found in the thoracic cords, the novel movements observed in the reconstructed brachial plexuses were in synchrony with respiration. These results suggested that the plasticity of central neural networks is limited between two widely separated areas, such as between the midcervical and midthoracic motor cortical areas in the present studies, and therefore, the efforts to reconstruct neural networks, both centrally and peripherally, should aim at rebuilding situations as nearly to the original status as possible. J. Comp. Neurol. 380:155–163, 1997.

Early Effects of Gamma Knife Surgery on Malignant and Benign Intracranial Tumors

To assess the early response of intracranial tumors to Gamma Knife surgery, we performed a prospective investigation of 42 patients treated by Gamma Knife surgery for different types of intracranial tumors. The clinical condition, tumor volume, treatment results and their temporal correlation with the irradiation were analyzed, based on MRI performed on the same MR scanner. Volume reduction in the tumors measured at the latest follow-up ranged from 0.2 to 100%. All except 1 malignant tumor showed decreasing size and improving peritumoral edema 1-7 months after radiosurgery. In 30 benign tumors, 13 showed either a decrease or no change in volume. However, an initial volume increase was observed in 17 tumors, with a maximum at 3-9 months, which subsequently regressed. In 2 meningioma patients, peritumoral edema increased and needed steroid treatment. Sequential PET-FDG imaging of the patients showed decreasing FDG uptake, indicating a decrease tumor in metabolism. The PET findings correlated well with the loss of contrast enhancement on MR images. In conclusion, intracranial tumors respond to Gamma Knife surgery from an early stage. Different tumors have different responses to radiosurgery. It is too early to offer a prognosis of long-term effects based on the limited material. However, sequential clinical, MR and PET follow-ups provide an excellent opportunity to investigate the evolving irradiation effects in vivo.

Stereotactic Internal Irradiation for Cystic Craniopharyngiomas: A 6-Year Experience

Fourteen adults and 4 children with cystic craniopharyngiomas were treated with stereotactic beta-irradiation during a 6-year period. Of these patients, 10 were primary cases, and 8 were recurrences after previous major surgery. Radioactive phosphorus (32P) or yttrium (90Y) in colloidal forms were used as the radiation agents. Cyst volumes (10-130 ml) were assessed intraoperatively by the 99Tc radiodilution method. According to our treatment program, the radiation dose to the cyst wall was 20,000 rad and the total irradiation time 2 weeks. The follow-up period ranged from 1 to 6 years, with an average of 3.8 years. Postoperative shrinkage of the cysts and clinical improvement were observed in most patients. Pertinent clinical data and results of treatment are described.

Direct puncture of the cavernous sinus for obliteration of a recurrent carotid-cavernous fistula.

The authors report direct transcutaneous puncture of the cavernous sinus through an intact orbit for embolization of a recurrent carotid-cavernous fistula (CCF) after 10 prior operations. The fistula was obliterated completely with this technique. No significant complication was noted except temporary ptosis for about 2 months. When other approaches are difficult or impossible, this technique can be an alternate way to treat a recurrent CCF after a trapping procedure.

Navigator system-assisted endoscopic fenestration of a symptomatic cyst in the septum pellucidum—technique and cases report

Expanding cysts of the septum pellucidum are rare and frequently manifest as intermittent headaches. Although the technique of endoscopic fenestration has been used since 1999, only a limited number of cases have been reported. We have added the use of a navigator system to guide keyhole creation and endoscopic access. To provide experience in navigator endoscopic treatment of symptomatic cyst of septum pellucidum and long-term follow-up of the surgical result. Under the guidance of the navigator system, a burr hole was made and rigid endoscope was inserted into the lateral ventricle through a working sheath. With direct visualization, only one side of the lateral wall of the cyst was fenestrated. And a grasping basket was used to further dilate the perforated hole. Patient A, a 14-year-old male adolescent, had an acute onset of severe headache with increased intracranial pressure. Patient B was a 37-year-old woman with a diagnosis of medically intractable migraine. Both patients experienced dramatic symptomatic relief after surgery at 4.5- and 2-year follow-up exams, respectively. The technique of navigator-assisted endoscopic fenestration in the treatment of a symptomatic cyst of the septum pellucidum might be a safe and effective method. It achieved satisfactory results in our two patients.

Posterior transarticular screw fixation for chronic atlanto-axial instability.

Treatment for chronic atlanto-axial instability remains problematic despite recent innovations in new surgical techniques and instrumentation. Our team reviewed a series of 23 cases of patients with chronic atlanto-axial instability who underwent posterior transarticular screw fixation operations between May 1998 and September 2002. Etiologies of these patients included failed prior surgery, rheumatoid arthritis, congenital anomalies and old odontoid fractures. The clinical presentations were nuchal pain and cervical myelopathy or radiculopathy, with sensory and/or motor deficits that persisted for more than 3 months. We routinely used external reduction to realign the C1-C2 axis prior to operating, and operated on patients using halo-vest fixation. After surgery, the halo-vest was replaced by a collar. In the post-operative follow-up, 22 of the 23 patients (96%) were found to have achieved solid, bony or fibrous union of the C1-C2 axis. Eleven of the 14 (79%) patients with pre-operative neck pain experienced immediate relief or significant improvement. Thirteen of the 20 patients (65%) with myelo-radiculopathy demonstrated improvement of previous motor deficits. Major morbidity included a vertebral artery (VA) injury and a malpositioned screw. No cases of mortality or neurological complications occurred in this series. Posterior transarticular C1-C2 screw fixation results in a high fusion rate without the additional need for rigid external immobilization. It allows good neurological recovery in cases of chronic atlanto-axial instability. Judicious pre-surgical planning and meticulous operative technique may avoid neurological complications and vertebral artery injury.

Cervical spinal stenosis and myelopathy due to atlas hypoplasia

This paper describes a patient who presented at our hospital with neurologic symptoms due to congenital cervical spinal stenosis at the atlas level. Congenital atlantal stenosis is usually due to hypoplasia of the posterior arch of the atlas. It is a rare cause of spinal stenosis, and only 12 symptomatic patients with isolated atlantal stenosis have been reported. Current treatment is surgical decompression, and all reported patients receiving surgical treatment improved to some degree.