Fusion Revision Surgery With Reamer-Irrigator-Aspirator to Harvest Autograft After Spinal Pseudarthrosis

Background and purpose

Spinal pseudarthrosis (SPA) is a common complication after attempted cervical or lumbosacral spinal fusion surgery. Revision surgeries usually necessitate bone graft implementation as an adjunct to hardware revision. Iliac crest bone graft is the gold standard but availability can be limited and usage often leads to persistent postoperative pain at the donor site. There is scant literature regarding the use of reamer-irrigator-aspirator (RIA)-harvested bone graft in lumbar spinal fusion. This is a collaborative study between orthopedic surgery and neurosurgery departments to utilize femur intramedullary autograft harvested using the RIA system as an adjunct graft in SPA revision surgeries.

Materials and methods

A retrospective review was conducted at a single center between August 2014 and December 2017 of patients aged ≥ 18 years and diagnosed with cervical, thoracic, or lumbar SPA who underwent revision fusion surgery using femur intramedullary autograft harvested using the RIA system. Plain radiographs and CT scans were utilized to confirm successful fusion.

Results

Eleven patients underwent 12 SPA revision surgeries using the RIA system as a source for bone graft in addition to bone morphogenetic protein 2 (BMP-2) and allograft. The mean amount of graft harvested was 51.3 mL (range: 20-70 mL). Nine patients achieved successful fusion (81.8%). The average time to fusion was 9.1 months. Four patients (36.4%) had postoperative knee pain. Regarding patient position and approach for harvesting, 66.7% (n = 8) of cases were positioned prone and a retrograde approach was utilized in 91.7% (n = 11) of cases.

Interpretation

This is the first case series in known literature to report the RIA system as a reliably considerable source of autologous bone graft for SPA revision surgeries. It provides a useful adjunct to the known types of bone grafts. Patient positioning and the approach choice for graft harvesting can be adjusted according to the fusion approach and the surgeon’s preference.

A computed tomography-based morphometric study of thoracic pedicle anatomy in a random United States trauma population

OBJECT

The objective of this study was to establish normative data for thoracic pedicle anatomy in the US adult population. To this end, CT scans chosen at random from an adult database were evaluated to determine the ideal pedicle screw (PS) length, diameter, trajectory, and starting point in the thoracic spine. The role of patient sex and side of screw placement were also assessed. The authors postulated that this information would be of value in guiding safe implant size and placement for surgeons in training.

METHODS

One hundred patients (50 males and 50 females) were selected via retrospective review of a hospital trauma registry database over a 6-month period. Patients included in the study were older than 18 years of age, had axial bone-window CT images of the thoracic spine, and had no evidence of spinal trauma. For each pedicle, the pedicle width, pedicle-rib width, estimated screw length, trajectory, and ideal entry point were measured using eFilm Lite software. Statistical analysis was performed using the Student t-test.

RESULTS

The shortest mean estimated PS length was at T-1 (33.9 ± 3.3 mm), and the longest was at T-9 (44.9 ± 4.4 mm). Pedicle screw length was significantly affected by patient sex; men could accommodate a PS from T1-12 a mean of 4.0 ± 1.0 mm longer than in women (p < 0.001). Pedicle width showed marked variation by spinal level, with T-4 (4.4 ± 1.1 mm) having the narrowest width and T-12 (8.3 ± 1.7 mm) having the widest. Pedicle width had an obvious affect on potential screw diameter; 65% of patients had a least 1 pedicle at T-4 that was < 5 mm in diameter and therefore would not accept a 4.0-mm screw with 1.0 mm of clearance, as compared with only 2% of patients with a similar status at T-12. Sex variation was also apparent, as thoracic pedicles from T-1 to T-12 were a mean of 1.4 ± 0.2 mm wider in men than in women (p < 0.001). The PS trajectory in the axial plane was measured, showing a marked decrease from T-1 to T-4, stabilization from T-5 to T-10, followed by a decrease at T11-12. When screw trajectory was stratified by side of placement, a mean of 1.7° ± 0.5° of increased medialization was required for ideal pedicle cannulation from T-3 to T-12 on the left as compared with the right side, presumably because of developmental changes in the vertebral body caused by the aorta (p < 0.05 for T3-12, except for T-5, where p = 0.051). The junction of the superior articular process, lamina, and the superior ridge of the transverse process was shown to be a conserved surface landmark for PS placement.

CONCLUSIONS

Preoperative CT evaluation is important in choosing PS length, diameter, trajectory, and entry point due to variation based on spinal level, patient sex, and side of placement. These data are valuable for resident and fellow training to guide the safe use of thoracic PSs.

A computed tomography-based feasibility study of translaminar screw fixation in the upper thoracic spine

OBJECT

Translaminar screws (TLSs) offer an alternative to pedicle screw (PS) fixation in the upper thoracic spine. Although cadaveric studies have described the anatomy of the laminae and pedicles at T1-2, CT imaging is the modality of choice for presurgical planning. In this study, the goal was to determine the diameter, maximal screw length, and optimal screw trajectory for TLS placement at T1-2, and to compare this information to PS placement in the upper thoracic spine as determined by CT evaluation.

METHODS

One hundred patients (50 men and 50 women), whose average age was 41.7 +/- 19.6 years, were selected by retrospective review of a trauma registry database over a 6-month period. Patients were included in the study if they were over the age of 18, had standardized axial bone-window CT imaging at T1-2, and had no evidence of spinal trauma. For each lamina and pedicle, width (outer cortical and cancellous), maximal screw length, and optimal screw trajectory were measured using eFilm Lite software. Statistical analysis was performed using the Student t-test.

RESULTS

The T-1 lamina was estimated to accommodate, on average, a 5.8-mm longer screw than the T-2 lamina (p < 0.001). At T-1, the maximal TLS length was similar to PS length (TLS: 33.4 +/- 3.6 mm, PS: 33.9 +/- 3.3 mm [p = 0.148]), whereas at T-2, the maximal PS length was significantly greater than the TLS length (TLS: 27.6 +/- 3.1 mm, PS: 35.3 +/- 3.5 mm [p < 0.001]). When the lamina outer cortical and cancellous width was compared between T-1 and T-2, the lamina at T-2 was, on average, 0.3 mm wider than at T-1 (p = 0.007 and p = 0.003, respectively). In comparison with the corresponding pedicle, the mean outer cortical pedicle width at T-1 was wider than the lamina by an average of 1.0 mm (lamina: 6.6 +/- 1.1 mm, pedicle: 7.6 +/- 1.3 mm [p < 0.001]). At T-2, however, outer cortical lamina width was wider than the corresponding pedicle by an average of 0.6 mm (lamina: 6.9 +/- 1.1 mm, pedicle: 6.3 +/- 1.2 mm [p < 0.001]). At T-1, 97.5% of laminae measured could accept a 4.0-mm screw with 1.0 mm of clearance, compared with 99.5% of T-1 pedicles; whereas at T-2, 99% of laminae met this requirement, compared with 94.5% of pedicles. The ideal screw trajectory was also measured (T-1: 49.2 +/- 3.7 degrees for TLS and 32.8 +/- 3.8 degrees for PS; T-2: 51.1 +/- 3.5 degrees for TLS and 20.5 +/- 4.4 degrees for PS).

CONCLUSIONS

Based on CT evaluation, there are no anatomical limitations to the placement of TLSs compared with PSs at T1-2. Differences were noted, however, in lamina length and width between T-1 and T-2 that must be considered when placing TLS at these levels.

DYSPHAGIA AND NEUROPATHIC FACIAL PAIN TREATED WITH MOTOR CORTEX STIMULATION

OBJECTIVE

We report on a patient with a neuropathic facial pain syndrome, including elements of trigeminal neuralgia, glossopharyngeal neuralgia, and dysphagia. After failing medical and surgical decompressive treatments, the patient underwent implantation of a motor cortex stimulation (MCS) system.

CLINICAL PRESENTATION

A 54-year-old woman presented with a 14-year history of left-sided facial pain, throat pain, and associated nausea and vomiting. The patient failed several open surgical and percutaneous procedures for her facial pain syndrome. Additionally, several medication trial attempts were unsuccessful. Imaging studies were normal.

INTERVENTION

The patient underwent placement of a right-sided MCS system for treatment of her neuropathic facial pain syndrome. The procedure was tolerated well, and the trial stimulator provided promising results. The permanent MCS generator needed to be reprogrammed at the time of the 5-week follow-up visit to optimize symptom relief. The patient demonstrated dramatic improvements in her neuropathic facial and oral pain, including improvements in swallowing toleration, after the 5-week follow-up examination with subthreshold MCS. A decline in treatment efficacy also occurred 2 years after implantation due to generator depletion. Symptom improvement returned with stimulation after the generator was replaced.

CONCLUSION

A novel implantable MCS system was used to treat this patient's neuropathic facial pain. Durable improvements were noted not only in her facial pain, but also in swallowing toleration. The ultimate role of MCS in the treatment of pain conditions is still not well-defined but might play a part in refractory cases and, as in this case, might improve other functional issues, including dysphagia.

Laminar screw fixation of the axis

Object

Laminar fixation of the axis with crossing bilateral screws has been shown to provide rigid fixation with a theoretically decreased risk of vertebral artery damage compared with C1–2 transarticular screw fixation and C-2 pedicle screw fixation. Some studies, however, have shown restricted rigidity of such screws compared with C-2 pedicle screws, and others note that anatomical variability exists within the posterior elements of the axis that may have an impact on successful placement. To elucidate the clinical impact of such screws, the authors report their experience in placing C-2 laminar screws in adult patients over a 2-year period, with emphasis on clinical outcome and technical placement.

Methods

Sixteen adult patients with cervical instability underwent posterior cervical and cervicothoracic fusion procedures at our institution with constructs involving C-2 laminar screws. Eleven patients were men and 5 were women, and they ranged in age from 28 to 84 years (mean 57 years). The reasons for fusion were degenerative disease (9 patients) and treatment of trauma (7 patients). In 14 patients (87.5%) standard translaminar screws were placed, and in 2 (12.5%) an ipsilateral trajectory was used. All patients underwent preoperative radiological evaluation of the cervical spine, including computed tomography scanning with multiplanar reconstruction to assess the posterior anatomy of C-2. Anatomical restrictions for placement of standard translaminar screws included a deeply furrowed spinous process and/or an underdeveloped midline posterior ring of the axis. In these cases, screws were placed into the corresponding lamina from the ipsilateral side, allowing bilateral screws to be oriented in a more parallel, as opposed to perpendicular, plane. All patients were followed for > 2 years to record rates of fusion, instrumentation failure, and other complications.

Results

Thirty-two screws were placed without neurological or vascular complications. The mean follow-up duration was 27.3 months. Complications included 2 revisions, one for pseudarthrosis and the other for screw pullout, and 3 postoperative infections.

Conclusions

Placement of laminar screws into the axis from the standard crossing approach or via an ipsilateral trajectory may allow a safe, effective, and durable means of including the axis in posterior cervical and cervicothoracic fusion procedures.

Thoracic kyphotic deformity reduction with a distractible titanium cage via an entirely posterior approach

OBJECTIVE

Surgical correction of thoracic kyphotic deformity is often associated with significant surgical and neurological morbidity and unsatisfactory reduction of kyphosis, especially in patients who cannot tolerate anterior thoracic procedures because of associated comorbidity. We describe a technique in which kyphotic deformity of the thoracic and thoracolumbar spine is corrected, decompressed, and stabilized with a circumferential fixation construct from a lone posterior approach.

METHODS

We reviewed the radiographic and clinical outcomes of seven patients undergoing vertebrectomy via a bilateral modified costotransversectomy approach followed by posterior placement of a distractible cage, reduction of the deformity via cage distraction, and supplemental dorsal instrumentation. All patients possessed thoracic/thoracolumbar kyphosis; however, a transthoracic approach was thought to be high risk because of medical comorbidity.

RESULTS

Seven patients underwent this procedure for thoracolumbar kyphosis resulting from a spinal tumor, osteomyelitis, and fracture. Vertebrectomies were performed at T2-T3, T4-T5, T5-T6, T12-L1, and L1. The mean preoperative kyphosis was 28.6 degrees, the mean postoperative kyphosis at the time of the final follow-up examination was 12.1 degrees, and the mean change in kyphosis was 53%. The mean long-term follow-up period was approximately 16 months. At the time of the final follow-up examination for all patients, there was no decline in neurological function, and pain management consisted of minimal use of oral narcotics.

CONCLUSION

This technique allows for circumferential decompression of the spinal cord via a posterior approach in patients with thoracic kyphotic deformities who cannot tolerate anterior thoracic approaches. In addition, in situ distraction of the expandable cage allows correction of sagittal imbalance and restores height without the potential loss of spinal height associated with osteotomies.

Translaminar screw fixation in the upper thoracic spine

Object

The use of pedicle screws (PSs) for instrument-assisted fusion in the cervical and thoracic spine has increased in recent years, allowing smaller constructs with improved biomechanical stability and repositioning possibilities. In the smaller pedicles of the upper thoracic spine, the placement of PSs can be challenging and may increase the risk of damage to neural structures. As an alternative to PSs, translaminar screws can provide spinal stability, and they may be used when pedicular anatomy precludes successful placement of PSs. The authors describe the technique of translaminar screw placement in the T-1 and T-2 vertebrae.

Methods

Seven patients underwent cervicothoracic fusion to treat trauma, neoplasm, or degenerative disease. Nineteen translaminar screws were placed, 13 at T-1 and six at T-2. A single asymptomatic T-2 screw violated the ventral laminar cortex and was removed.

The mean clinical and radiographic follow up exceeded 14 months, at which time there were no cases of screw pull-out, screw fracture, or progressive kyphotic deformity.

Conclusions

Rigid fixation with translaminar screws offers an attractive alternative to PS fixation, allowing the creation of sound spinal constructs and minimizing potential neurological morbidity. Their use requires intact posterior elements, and care should be taken to avoid violation of the ventral laminar wall.

Intracranial aneurysm following radiation therapy during childhood for a brain tumor. Case report and review of the literature

Ionizing radiation therapy is associated with pathological vascular changes in intracranial vessels, most commonly in the form of vessel thrombosis and occlusion. The development of an intracranial aneurysm following such therapy, however, is far less common. In this report the authors describe a 24-year-old man in whom a distal middle cerebral artery aneurysm developed 15 years after radiotherapy, which was given as adjuvant treatment following resection of a medulloblastoma. The patient underwent a craniotomy for microsurgical trapping of the aneurysm and was discharged without any neurological deficit. This case serves to remind clinicians of the possibility, albeit rare, that intracranial aneurysms may form following cranial radiotherapy.

Preoperative imaging of cervical spine hemangioblastomas using three-dimensional fusion digital subtraction angiography

✓ Angiography is often performed to identify the vascular supply of hemangioblastomas prior to resection. Conventional two-dimensional (2D) digital subtraction (DS) angiography and three-dimensional (3D) DS angiography provides high-resolution images of the vascular structures associated with these lesions. However, such 3D DS angiography often does not provide reliable anatomical information about nearby osseous structures, or when it does, resolution of vascular anatomy in the immediate vicinity of bone is sacrificed. A novel angiographic reconstruction algorithm was recently developed at The Johns Hopkins University to overcome these inadequacies. By combining two separate sequences of images of bone and blood vessels in a single 3D representation, 3D fusion DS (FDS) angiography provides precise topographic information about vascular lesions in relation to the osseous environment, without a loss of resolution.

In this paper, the authors present the cases of two patients with cervical spine hemangioblastomas who underwent preoperative evaluation with FDS angiography and then successful gross-total resection of their tumors. In both cases, FDS angiography provided high-resolution 3D images of the hemangioblastoma anatomy, including each tumor’s topographic relationship with adjacent osseous structures and the location and size of feeding arteries and draining veins. These cases provide evidence that FDS angiography represents a useful adjunct to magnetic resonance imaging and 2D DS angiography in the preoperative evaluation and surgical planning of patients with vascular lesions in an osseous environment, such as hemangioblastomas in the spinal cord.

Concomitant Conus Medullaris Ependymoma and Filum Terminale Lipoma: Case Report

OBJECTIVE:

Ependymomas of the conus medullaris-cauda equina-filum terminale region are typically solitary lesions. In this report, we describe the clinical presentation, radiographic findings, operative details, and pathological features of a patient with a conus medullaris ependymoma and a filum terminale lipoma.

CLINICAL PRESENTATION:

A 40-year-old woman presented with increasing low back pain and bowel and bladder dysfunction. Magnetic resonance imaging revealed a partially cystic enhancing lesion at the conus medullaris and a T1-weighted hyperintense mass within the filum terminale.

INTERVENTION:

An L2-L3 laminotomy/laminoplasty was performed for gross total resection of the mass. Histopathological examination demonstrated a conus medullaris ependymoma and filum terminale lipoma. The patient experienced complete resolution of her preoperative symptoms.

CONCLUSION:

Spinal cord ependymomas are almost exclusively single lesions and their coexistence with other pathological entities is rare. In this report, we describe a patient with a concomitant conus medullaris ependymoma and filum terminale lipoma.

Frameless stereotaxy in a transmandibular, circumglossal, retropharyngeal cervical decompression in a Klippel-Feil patient: technical note

Frameless stereotaxy, while most commonly applied to intracranial surgery, has seen an increasing number of applications in spinal surgery. Its use in the spine has been described to a greater degree in posterior rather than anterior surgical approaches, presumably due to the relative paucity of anatomical landmarks appropriate for frameless stereotactic registration in the anterior spine. This technical note illustrates the previously undescribed, successful use of frameless stereotaxy to the transmandibular, circumglossal, retropharyngeal surgical approach in a patient with Klippel-Feil syndrome.

A Novel Intravertebral Tumor Model in Rabbits

OBJECTIVE

Although the majority of human epidural spinal metastases originate in the vertebral body, current animal models of spinal epidural tumors are limited to extraosseous tumor placement. We investigated the onset of paraparesis, radiographic changes (magnetic resonance imaging [MRI] and computed tomographic [CT] scans), and histopathological findings after intraosseous injection of VX2 carcinoma cells into the lower thoracic vertebrae of rabbits.

METHODS

New Zealand white rabbits (n = 23) were injected with a 15-mul suspension containing 300,000 VX2 carcinoma cells in the lowest thoracic vertebral body. Lower extremity motor function was assessed daily. For the first 3 animals, MRI scans (T2-weighted and T1-weighted +/- gadolinium) were acquired at postoperative day (POD) 14 and at the onset of paraparesis. Noncontrast CT scans were obtained on POD 7 and at the time of paraparesis. At the onset of paraparesis, the animals ware killed and the spines were dissected. After demineralization, hematoxylin and eosin cross sections were obtained.

RESULTS

Before the onset of paraparesis, the CT and MRI scans revealed no gross tumor. At the onset of paraparesis, CT scans demonstrated an osteolytic tumor centered at the junction of the left pedicle and vertebral body, and MRI scans demonstrated epidural tumor arising from the body and compressing the spinal cord. Histopathological examination confirmed carcinoma arising from the body and extending into the canal, with widespread osteolytic activity. By POD 28, 72% of the animals had become paraparetic, and by the termination of the experiment on POD 120, 89% had become paraparetic.

CONCLUSION

We established a novel intraosseous intravertebral tumor model in rabbits and characterized it with respect to onset of paraparesis, imaging features, and histopathological findings.

Ventriculoperitoneal shunt malfunction presenting with pleuritic chest pain

BACKGROUND

Ventriculoperitoneal (VP) shunts are widely used for treating hydrocephalus. These devices are prone to malfunction with up to 70% requiring revision. Shunt infection and obstruction comprise the majority of malfunctions and usually present dramatically. However, rare presentations occur.

METHODS/RESULTS

We report a rare case of VP shunt malfunction presenting with pleuritic chest pain. A 13-year-old girl with a VP shunt placed at birth for congenital hydrocephalus presented on multiple occasions with pleuritic chest pain, cough, and fever. She was diagnosed with an upper respiratory tract infection and discharged home. She returned with respiratory compromise, and chest x-ray depicted the shunt catheter in the pleural space with an associated pleural effusion and infiltrate. The patient fully recovered with intravenous antibiotics, thoracentesis, and placement of a new shunt system.

CONCLUSIONS

VP shunt malfunction usually presents with signs and symptoms of increased intracranial pressure and/or infection. However, unusual presentations of malfunction may occur with signs and symptoms which appear unrelated to the shunt. Thus, all patients with VP shunts warrant a comprehensive evaluation.

Spinal angiolipoma: case report and review of the literature

Spinal angiolipomas are rare lesions usually found in the epidural space of the thoracic spine. This report presents a case of and reviews the literature on this rare entity. The etiology, clinical presentation, imaging, and treatment are discussed. In 92 reported cases of spinal angiolipoma 56 occurred in women (61%), and 36 in men (39%). Mean age of occurrence is 42.9 years (range 10 days-85 years) with most patients presenting with slowly progressive symptoms of spinal cord compression. Most cases occur in the extradural compartment, and are of the non-invasive subtype. This rare clinical entity must be considered in the differential diagnosis of spinal epidural lesions. In most cases complete removal is possible, however, prognosis is good even for infiltrating lesions. Thus, one must not risk neurological damage to attain complete resection.

Outcome and cost of craniotomy performed to treat tumors in regional academic referral centers

OBJECTIVE

Improved clinical and economic outcomes for high-risk surgical procedures have been previously cited in support of regionalization. The goal of this study was to examine the effects of regionalization by analyzing the cost and outcome of craniotomy for tumors and to compare the findings in academic medical centers versus community-based hospitals.

METHODS

Outcomes and charges were analyzed for all adult patients undergoing craniotomy for tumor in 33 nonfederal acute care hospitals in Maryland using the Maryland Health Service Cost Review Commission database for the years 1990 to 1996. A total of 4723 patients who underwent craniotomy for tumor were selected on the basis of Diagnostic Related Group 1 (craniotomy except for trauma, age 18 or older) and International Classification of Diseases-9th Revision diagnosis code for benign tumor, primary malignant neoplasm, or secondary malignant neoplasm (codes 191, 192, 194, 200, 225, 227, 228, 237, and 239). Hospitals were categorized as high-volume hospitals (>50 craniotomies/yr) or low-volume hospitals (<or=50 craniotomies/yr). In-hospital mortality, length of stay, and charges were evaluated.

RESULTS

The mortality rate was 2.5% at high-volume centers and 4.9% at low-volume hospitals with an adjusted relative risk of 1.4 (P < 0.05), assuming equivalence of disease severity. Adjusted average length of stay in high-volume centers was 6.8, as compared with 8.8 days in low-volume hospitals (P < 0.001). Adjusted average total charges were $15,867 at high-volume centers and $14,045 at low-volume centers (P < 0.001). If all patients in the state had been treated at centers with survival rates equal to those achieved by the high-volume centers, then 46 patients would not have died of operation; that is, 48.6% fewer patients would have died, at an additional adjusted cost of $76,395 dollars per patient saved.

CONCLUSION

High-volume regional medical centers are capable of providing services with improved mortality rates and fewer hospital days, although with adjusted costs slightly higher than those at low-volume hospitals.

Outcome and Cost of Craniotomy Performed to Treat Tumors in Regional Academic Referral Centers

OBJECTIVE

Improved clinical and economic outcomes for high-risk surgical procedures have been previously cited in support of regionalization. The goal of this study was to examine the effects of regionalization by analyzing the cost and outcome of craniotomy for tumors and to compare the findings in academic medical centers versus community-based hospitals.

METHODS

Outcomes and charges were analyzed for all adult patients undergoing craniotomy for tumor in 33 nonfederal acute care hospitals in Maryland using the Maryland Health Service Cost Review Commission database for the years 1990 to 1996. A total of 4723 patients who underwent craniotomy for tumor were selected on the basis of Diagnostic Related Group 1 (craniotomy except for trauma, age 18 or older) and International Classification of Diseases–9th Revision diagnosis code for benign tumor, primary malignant neoplasm, or secondary malignant neoplasm (codes 191, 192, 194, 200, 225, 227, 228, 237, and 239). Hospitals were categorized as high-volume hospitals (&gt;50 craniotomies/yr) or low-volume hospitals (≤50 craniotomies/yr). In-hospital mortality, length of stay, and charges were evaluated.

RESULTS

The mortality rate was 2.5% at high-volume centers and 4.9% at low-volume hospitals with an adjusted relative risk of 1.4 (P &lt; 0.05), assuming equivalence of disease severity. Adjusted average length of stay in high-volume centers was 6.8, as compared with 8.8 days in low-volume hospitals (P &lt; 0.001). Adjusted average total charges were $15,867 at high-volume centers and $14,045 at low-volume centers (P &lt; 0.001). If all patients in the state had been treated at centers with survival rates equal to those achieved by the high-volume centers, then 46 patients would not have died of operation; that is, 48.6% fewer patients would have died, at an additional adjusted cost of $76,395 dollars per patient saved.

CONCLUSION

High-volume regional medical centers are capable of providing services with improved mortality rates and fewer hospital days, although with adjusted costs slightly higher than those at low-volume hospitals.

Decompressive craniectomy for intractable cerebral edema: experience of a single center

Several case reports and small clinical series have reported benefits of decompressive hemicraniectomy in patients with intractable cerebral edema and early clinical herniation. Specific indications and timing for this intervention remain unclear. We present our experience with this procedure in a subset of 18 patients with massive cerebral edema refractory to medical management, treated with decompressive craniectomy over a 3-year period (1997 to 2000). Computerized tomography (CT) scans were independently analyzed by a neuroradiologist blinded to clinical outcome. Eleven male and seven female patients, ages 20 to 69 years (mean +/- SEM, 46 +/- 14 years), underwent hemicraniectomy for the following diagnoses: 12 hemispheric infarcts, 3 traumatic intracerebral hemorrhages/contusions, 2 nontraumatic intraparenchymal hemorrhages (ICH), and 1 subdural empyema. This population included four patients with aneurysmal subarachnoid hemorrhage (SAH). Patients were followed for a mean of 10 months. Clinical factors including age, side of lesion, preoperative herniation signs, and early surgery (<12 or <24 hours) were not significantly associated with mortality or Glasgow outcome score (GOS). Preoperative CT evidence of transtentorial herniation (present in 5/17 patients) was associated with mortality ( = 0.04), while preoperative uncal herniation (8/17 patients) was associated with poor outcome (GOS > 1) ( = 0.01). Favorable outcome (GOS > 3) occurred in six patients, three with spontaneous or traumatic focal hematomas. Of four patients with SAH, one died while the others were severely disabled (GOS 3). Seven of nine patients with malignant MCA infarctions unrelated to SAH had poor outcomes. The overall mortality was 4/18 (22%). Patients with refractory cerebral swelling secondary to focal hematomas may have better outcomes following decompressive craniectomy. Patients with preexisting SAH seem to have poor outcomes, possibly related to other neurologic comorbidities. Hemicraniectomy requires definition of proper timing. Preoperative CT findings, especially transtentorial and uncal herniation may be useful in defining when decompressive surgery should not be performed.

Intraoperative microelectrode and semi-microelectrode recording during the physiological localization of the thalamic nucleus ventral intermediate

We review the techniques of physiological localization of the site for ventralis intermedius (Vim) thalamotomy or implantation of Vim-deep brain stimulation (DBS) for treatment of parkinsonian, essential, and intention tremor. Both microelectrode and semi-microelectrode techniques are reviewed. We believe the use of microelectrode and semi-microelectrode recordings in combination with Radiological landmarks provide the most accurate localization of the target. In addition to recording, microstimulation of subcortical structures such as Vim and thalamic nucleus ventralis caudal through the microelectrode may improve physiological identification by altering the tremor and evoking somatic sensations, respectively. Microelectrode recording provides the highest resolution picture of the target site at a cost of increased time to locate the target. We also review the relationship between thalamic neuronal firing and electromyographic activity during tremor. Implications of these results for the mechanisms for parkinsonian, essential, and intention tremors are discussed.

Ectopic recurrence of craniopharyngioma after an interhemispheric transcallosal approach: case report

OBJECTIVE AND IMPORTANCE

Ectopic recurrence of a craniopharyngioma is a rare postoperative complication. We present a case of a craniopharyngioma that ectopically recurred along the tract of a previous surgical route.

CLINICAL PRESENTATION

A 73-year-old female patient presented 8 years earlier with a suprasellar craniopharyngioma. She underwent a right frontal craniotomy, with an interhemispheric transcallosal approach, for total microsurgical resection of the tumor. No postoperative radiotherapy was administered. Four years after surgery, magnetic resonance imaging studies revealed a well-circumscribed, heterogeneously enhancing, parasagittal mass with significant vasogenic edema in the right frontal lobe. Enlargement of the lesion was noted in subsequent radiological evaluations until 8 years after surgery, when the patient experienced a significant decline in neurocognitive status and the mass was surgically resected.

INTERVENTION

Gross total resection of a histologically confirmed craniopharyngioma was achieved.

CONCLUSION

To our knowledge, only eight previous case reports described the ectopic recurrence of a craniopharyngioma. Transplantation of tumor cells along the tract of a previous surgical route in six cases and dissemination in cerebrospinal fluid in two cases are presumed to be the primary mechanisms by which these ectopic recurrences occurred. The results of our literature review led us to conclude that total surgical resection, combined with careful inspection and irrigation of the surgical field, is the optimal treatment for preventing ectopic recurrences. Furthermore, it is recommended that, after primary craniopharyngioma resection, patients undergo long-term clinical and radiological follow-up monitoring for the rare development of an ectopically recurring tumor.

Microelectrode studies of normal organization and plasticity of human somatosensory thalamus

Microelectrode studies of single units in the human thalamus during stereotactic surgery offer a unique opportunity to study the organization and plasticity of the sensory thalamus. In this review the authors present results using single-unit microelectrode recording in the mapping of human sensory thalamus in a variety of patients. First they outline the overall organization of the human sensory thalamus, including both somatosensory and pain pathways. They also show that the sensory maps for receptive and projection fields can be altered during pathologic states such as amputation and spinal transection. Additionally, the sensory maps show plasticity during states with abnormal patterns of motor activity, like dystonia. Lastly, they discuss the processing of painful and emotionally laden sensory experiences through the thalamus. The physiologic results of thalamic pain processing are discussed in relation to the sensory-limbic model of pain. The studies reviewed demonstrate the spectrum of stimulus processing and plasticity of both painful and nonpainful signals by the human thalamus.

Neuronal activity in the region of the thalamic principal sensory nucleus (ventralis caudalis) in patients with pain following amputations

Thalamic neuronal activity has not been studied in a primate model of peripheral nerve injury. We now report neuronal activity in the region of the human principal sensory nucleus of thalamus (ventralis caudalis) in awake patients during the physiologic exploration that precedes surgical procedures for treatment of stump pain and movement disorders. All patients with amputations showed increased thalamic representations of the stump as reflected in both receptive and projected field maps. This suggested that thalamic re-organization involved both the afferent inputs from and the perceptual representation of the limb. The spontaneous activity of neurons in the region of ventralis caudalis representing the limb with the stump (stump area) was significantly different from that in other areas of the region of ventralis caudalis in patients with amputations (stump control areas) and in patients with movement disorders (control areas). The mean interspike intervals were significantly shorter for cells located in stump areas than for those located in stump control or control areas. Cells in all areas were found to fire in three different patterns: B group (burst) characterized by bursting activity, R group (relay) characterized as a Poisson process, and III group characterized by non-bursting, non-Poisson activity. Cells in the B group were significantly more common in stump control (41%) and stump areas (33%) than in control areas (15%). Bursting cells were found to have patterns consistent with the occurrence of a calcium spike (spike-burst pattern). The spike-burst pattern was most common among cells with receptive fields in the stump area. In these cells firing between bursts (primary event rate) was significantly higher than other cells in the region of ventralis caudalis, suggesting that spike-bursts are not due to hyperpolarization, i.e. low-threshold spikes. Spike-bursts often occur as a result of low-threshold spikes, when the cell is hyperpolarized. In contrast, spike-bursts in these patients were associated with increased interburst firing rates in cells with receptive fields. Thus bursting of these cells may have been due to high-threshold dendritic calcium spikes evoked by afferent input. In that case bursting could be involved in activity-dependent changes in thalamic function following deafferentation through a calcium-mediated mechanism.