Walter J. Jermakowicz

Experience with 25 years of dorsal root entry zone lesioning at a single institution.

Background: The authors sought to assess long-term efficacy, surgical morbidity, and postoperative quality of life in patients who have undergone dorsal root entry zone (DREZ) lesioning. Methods: We utilized the electronic chart system at our institution to identify patients who underwent DREZ lesioning since 1986. Of the patients that were able to be identified, 19 (12 males and 7 females) patients were able to be contacted at time of data collection. The mean age was 47 years (ranging from 23 to 70 years) with average preoperative pain duration of 12.5 years and average follow-up of 4.9 years. Results: Of the 19 patients we were able to contact, 7 (37%) patients experienced “excellent” postoperative (complete) pain relief with another 6 (32%) reporting “good” improvement. Three (16%) patients reported “mild” pain relief, while three (16%) patients reported poor results. Sixteen patients (84%) stated they would undergo DREZ lesioning again, if given a choice. Two patients (11%) had objective evidence of a new, mild motor deficit postoperatively. More than half of the patients, who answered, reported “good” quality of life. Two-sample unequal variance t-test showed no statistically significant difference in pain improvement between brachial plexus avulsion and end-zone spinal cord injury pain. Conclusion: With appropriate patient selection, DREZ lesioning is an efficacious and durable procedure that can be performed with low morbidity and good patient outcomes.

Intrinsic signal optical imaging evidence for dorsal V3 in the prosimian galago (Otolemur garnettii)

Currently, we lack consensus regarding the organization along the anterior border of dorsomedial V2 in primates. Previous studies suggest that this region could be either the dorsomedial area, characterized by both an upper and a lower visual field representation, or the dorsal aspect of area V3, which only contains a lower visual field representation. We examined these proposals by using optical imaging of intrinsic signals to investigate this region in the prosimian galago (Otolemur garnettii). Galagos represent the prosimian radiation of surviving primates; cortical areas that bear strong resemblances across members of primates provide a strong argument for their early origin and conserved existence. Based on our mapping of horizontal and vertical meridian representations, visuotopy, and orientation preference, we find a clear lower field representation anterior to dorsal V2 but no evidence of any upper field representation. We also show statistical differences in orientation preference patches between V2 and V3. We additionally supplement our imaging results with electrode array data that reveal differences in the average spatial frequency preference, average temporal frequency preference, and sizes of the receptive fields between V1, V2, and V3. The lack of upper visual field representation along with the differences between the neighboring visual areas clearly distinguish the region anterior to dorsal V2 from earlier visual areas and argue against a DM that lies along the dorsomedial border of V2. We submit that the region of the cortex in question is the dorsal aspect of V3, thus strengthening the possibility that V3 is conserved among primates. J. Comp. Neurol., 2012.

Findings on Preoperative Brain MRI Predict Histopathology in Children with Cerebellar Neoplasms

Background/Aims: The majority of pediatric patients with cerebellar neoplasms harbor pilocytic astrocytomas (PAs), medulloblastomas, or ependymomas. Knowledge of a preoperative likelihood of histopathology in this group of patients has the potential to influence many aspects of care. Previous studies have demonstrated hyperintensity on diffusion-weighted imaging to correlate with medulloblastomas. Recently, measurement of T2-weighted signal intensity (T2SI) was shown to be useful in identification of low-grade cerebellar neoplasms. The goal of this study was to assess whether objective findings on these MRI sequences reliably correlated with the underlying histopathology. Methods: We reviewed the radiologic findings of 50 pediatric patients who underwent resection of a cerebellar neoplasm since 2003 at our institution. Region of interest placement was used to calculate the relative diffusion-weighted signal intensity (rDWSI) and relative T2SI (rT2SI) of each neoplasm. Results: Tukey’s multiple comparison test demonstrated medulloblastomas to have significantly higher rDWSIs than PAs/ependymomas, and PAs to have significantly higher rT2SIs than medulloblastomas/ependymomas. A simple method consisting of sequential measurement of rDWSI and rT2SI to predict histopathology was then constructed. Using this method, 39 of 50 (78%) tumors were accurately predicted. Conclusion: Measurement of rDWSI and rT2SI using standard MRI of the brain can be used to predict histopathology with favorable accuracy in pediatric patients with cerebellar tumors.

Subacute cystic expansion of intracranial juvenile psammomatoid ossifying fibroma

Juvenile psammomatoid ossifying fibroma (JPOF) is a benign fibro-osseous lesion typically associated with the jaw, paranasal region, or orbit. However, JPOF may also originate from the skull base and locally invade the cranium. In published reports, intracranial JPOFs constitute only a small percentage of cases, and therefore it is not known whether more aggressive behavior typifies this distinct population of JPOFs compared with those in other locations. Nevertheless, JPOF histopathology is characterized by a number of active processes, including cystic transformation, that may precipitate violation of skull base boundaries. In the following article, the authors present a case of skull base JPOF that underwent cystic expansion in a young girl, produced a focal neurological deficit, and was resolved using a staged surgical approach.

Suppression of thalamocortical oscillations following traumatic brain injury in rats

OBJECT Traumatic brain injury (TBI) often causes an encephalopathic state, corresponding amplitude suppression, and disorganization of electroencephalographic activity. Clinical recovery in patients who have suffered TBI varies, and identification of patients with a poor likelihood of functional recovery is not always straightforward. The authors sought to investigate temporal patterns of electrophysiological recovery of neuronal networks in an animal model of TBI. Because thalamocortical circuit function is a critical determinant of arousal state, as well as electroencephalography organization, these studies were performed using a thalamocortical brain slice preparation. METHODS Adult rats received a moderate parietal fluid-percussion injury and were allowed to survive for 1 hour, 2 days, 7 days, or 15 days prior to in vitro electrophysiological recording. Thalamocortical brain slices, 450-μm thick, were prepared using a cutting angle that preserved reciprocal connections between the somatosensory cortex and the ventrobasal thalamic complex. RESULTS Extracellular recordings in the cortex of uninjured control brain slices revealed spontaneous slow cortical oscillations (SCOs) that are blocked by (2R)-amino-5-phosphonovaleric acid (50 μM) and augmented in low [Mg2+]o. These oscillations have been shown to involve simultaneous bursts of activity in both the cortex and thalamus and are used here as a metric of thalamocortical circuit integrity. They were absent in 84% of slices recorded at 1 hour postinjury, and activity slowly recovered to approximate control levels by Day 15. The authors next used electrically evoked SCO-like potentials to determine neuronal excitability and found that the maximum depression occurred slightly later, on Day 2 following TBI, with only 28% of slices showing evoked activity. In addition, stimulus intensities needed to create evoked SCO activity were elevated at 1 hour, 2 days, and 7 days following TBI, and eventually returned to control levels by Day 15. The SCO frequency remained low throughout the 15 days following TBI (40% of control by Day 15). CONCLUSIONS The suppression of cortical oscillatory activity following TBI observed in the rat model suggests an injury-induced functional disruption of thalamocortical networks that gradually recovers to baseline at approximately 15 days postinjury. The authors speculate that understanding the processes underlying disrupted thalamocortical circuit function may provide important insights into the biological basis of altered consciousness following severe head injury. Moreover, understanding the physiological basis for this process may allow us to develop new therapies to enhance the rate and extent of neurological recovery following TBI.

Microvascular Decompression: Salient Surgical Principles and Technical Nuances

Trigeminal neuralgia is a disorder associated with severe episodes of lancinating pain in the distribution of the trigeminal nerve. Previous reports indicate that 80-90% of cases are related to compression of the trigeminal nerve by an adjacent vessel. The majority of patients with trigeminal neuralgia eventually require surgical management in order to achieve remission of symptoms. Surgical options for management include ablative procedures (e.g., radiosurgery, percutaneous radiofrequency lesioning, balloon compression, glycerol rhizolysis, etc.) and microvascular decompression. Ablative procedures fail to address the root cause of the disorder and are less effective at preventing recurrence of symptoms over the long term than microvascular decompression. However, microvascular decompression is inherently more invasive than ablative procedures and is associated with increased surgical risks. Previous studies have demonstrated a correlation between surgeon experience and patient outcome in microvascular decompression. In this series of 59 patients operated on by two neurosurgeons (JSN and PEK) since 2006, 93% of patients demonstrated substantial improvement in their trigeminal neuralgia following the procedure—with follow-up ranging from 6 weeks to 2 years. Moreover, 41 of 66 patients (approximately 64%) have been entirely pain-free following the operation. In this publication, video format is utilized to review the microsurgical pathology of this disorder. Steps of the operative procedure are reviewed and salient principles and technical nuances useful in minimizing complications and maximizing efficacy are discussed.

Long-Term Clinical and Radiographic Stability After Clip Reconstruction of a Midbasilar Dissecting Mycotic Aneurysm

OBJECTIVE Mycotic aneurysm rupture has been described as a rare, universally fatal complication of central nervous system Coccidioides immitis meningitis. Recently, however, we reported the successful surgical management of a midbasilar dissecting mycotic aneurysm related to C. immitis meningitis in a 24-year-old pregnant woman with acquired immune deficiency syndrome. METHODS A 24-year-old pregnant woman with known acquired immune deficiency syndrome and a history of C. immitis meningitis presented to our institution with subarachnoid and intraventricular hemorrhage. Diagnostic cerebral angiography revealed a dissecting, midbasilar aneurysm involving the right anterior inferior cerebellar artery and causing stenosis of the proximal basilar artery. Through a retrosigmoid craniotomy, clip reconstruction of the basilar artery under hypothermic circulatory arrest was performed. The patient was neurologically intact at discharge (postoperative day 19) with the exception of mild disconjugate gaze and headache. RESULTS At her 53-month follow-up, the patient was neurologically intact with only mild disconjugate gaze on upgaze. There was no evidence of local aneurysm recurrence or regional aneurysm formation, and the basilar artery was patent. Her C. immitis meningitis was well controlled. The patient is maintained on oral highly active antiretroviral therapy and an antifungal regimen. CONCLUSIONS Our patient represents the only survivor of a C. immitis mycotic aneurysm rupture. In her case, long-term clinical and radiographic stability were achieved through a vigilant multidisciplinary approach.

Cognard Type V intracranial dural arteriovenous fistula presenting in a pediatric patient with rapid, progressive myelopathy

Cognard Type V dural arteriovenous fistulas (dAVFs) are a unique type of cranial vascular malformation characterized by congestion of the perimedullary venous system that may lead to devastating spinal cord pathology if left untreated. The authors present the first known case of a pediatric patient diagnosed with a Type V dAVF. A 14-year-old girl presented with a 3-week history of slowly progressive unilateral leg weakness that quickly progressed to bilateral leg paralysis, sphincter dysfunction, and complete sensory loss the day of her presentation. MRI revealed an extensive T2 signal change in the cervical spine and tortuous perimedullary veins along the entire length of the cord. An emergency cranial angiogram showed a Type V dAVF fed by the posterior meningeal artery with drainage into the perimedullary veins of the cervical spine. The fistula was not amenable to embolization because vascular access was difficult; therefore, the patient underwent urgent suboccipital craniotomy and ligation of the arterialized venous drainage from the fistula. The patients clinical course immediately reversed; she had a complete recovery over the course of a year, and she remains asymptomatic at the 2-year follow-up. This report adds to a growing body of evidence that describes the diverse and unpredictable nature of Type V dAVFs and highlights the need to obtain a cranial angiogram in pediatric patients with unexplained myelopathy and cervical cord T2 signal change on MRI.

158 Experience with Fifteen Years of Dorsal Root Entry Zone (DREZ) Lesioning at a Single Institution

INTRODUCTION: Dorsal root entry-zone (DREZ) lesioning is an important tool in the neurosurgeon’s armamentarium for treatment of medically-refractory chronic pain syndromes associated with deafferentation of neurons located in the superficial Rexed layers of the spinal cord. The objective of this study was to retrospectively review the past 15 years of DREZ procedures by a single neurosurgeon to provide insight about morbidity, outcome, microsurgical anatomy, and operative nuances associated with the technique.

What Language is Spoken Here? Conversations Between Neurons in Primate Visual Cortex

In this review we summarize results of our recent studies examining the role of spike timing between cells across early primate visual areas. Using methods that allowed us to examine spike timing between both pairs and larger groups of neurons we provide evidence that spike timing may be an important mechanism for propagating feed forward signals between the primary, secondary and tertiary cortical visual areas and that the propagation of this form of local cooperativity in the network is supported by oscillatory activity in the gamma frequency range.