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George M. Ibrahim, Benjamin W. Barry, Aria Fallah, O. Carter Snead III, James M. Drake, James T. Rutka, and Mark Bernstein

Epilepsy is a common childhood condition associated with a considerable medical and psychosocial burden. Children in whom medical treatment fails to reduce seizure burden represent an especially vulnerable patient population because prolonged, uncontrolled seizures are associated with poor developmental and neurocognitive outcomes. Surgical treatment in the form of cortical resection, functional disconnection, or neuromodulation may alleviate or significantly reduce the disease burden for a subset of these patients. However, there remains a dichotomy between the perceived benefits of surgery and the implementation of surgical strategies in the management of medically intractable epilepsy. The current paper presents an analysis of the bioethical implications of existing inequities in access to pediatric epilepsy surgery that result from inconsistent referral practices and discrepant evaluation techniques. The authors provide a basic bioethical framework composed of 5 primary expectations to inform public, institutional, and personal policies toward the provision of epilepsy surgery to afflicted children.

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James M. Drake

✓The tethered spinal cord is a fascinating yet controversial condition seen frequently in neurosurgical practice. Treatment decision making is made difficult by the variety of lesions and clinical presentations comprised by this condition and the absence of high-quality clinical outcome data to provide guidance. Clinical presentations may be divided into four general categories or typical scenarios: 1) significant dysraphic abnormality, clear clinical deterioration; 2) significant dysraphic abnormality, clinically normal or stable deficit; 3) incidentally discovered abnormality, other problem; and 4) tethered spinal cord symptomatology, normal imaging. The author provides case examples to illustrate potential treatment approaches and suggests balancing the risks and benefits for each general category.

Clearer diagnostic and treatment strategies for the tethered spinal cord will only result from high-quality clinical and basic research. Until the results of such research are available, surgeons should endeavor to maximize benefit and reduce risk for patients who may have a tethered spinal cord, walking the fine line between over- and undertreatment.

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Yuzuru Tashiro, Shushovan Chakrabortty, James M. Drake, and Toshiaki Hattori

The authors investigated functional neuronal changes in experimental hydrocephalus using immunohistochemical techniques for glutamic acid decarboxylase (GAD) and two neuronal calcium-binding proteins: parvalbumin (PV) and calbindin D28K (CaBP).

Hydrocephalus was induced in 16 adult Wistar rats by intracisternal injection of a kaolin solution, which was confirmed microscopically via atlantooccipital dural puncture. Four control rats received the same volume of sterile saline. Immunohistochemical staining for GAD, PV, and CaBP and Nissl staining were performed at 1, 2, 3, and 4 weeks after the injection. Hydrocephalus occurred in 90% of kaolin-injected animals with various degrees of ventricular dilation. In the cerebral cortex, GAD-, PV-, and CaBP-immunoreactive (IR) interneurons initially lost their stained processes together with a concomitant loss of homogeneous neuropil staining, followed by the reduction of their total number. With progressive ventricular dilation, GAD- and PV-IR axon terminals on the cortical pyramidal cells disappeared, whereas the number of CaBP-IR pyramidal cells decreased, and ultimately in the most severe cases of hydrocephalus, GAD, PV, and CaBP immunoreactivity was almost entirely diminished. In the hippocampus, GAD-, PV-, and CaBP-IR interneurons demonstrated a reduction of their processes and terminals surrounding the pyramidal cells, with secondary reduction of CaBP-IR pyramidal and granular cells. On the other hand, Nissl staining revealed almost no morphological changes induced by ischemia or neuronal degeneration even in the most severe cases of hydrocephalus.

Hydrocephalus results in the progressive functional impairment of GAD-, PV-, and CaBP-IR neuronal systems in the cerebral cortex and hippocampus, often before there is evidence of morphological injury. The initial injury of cortical and hippocampal interneurons suggests that the functional deafferentation from intrinsic projection fibers may be the initial neuronal event in hydrocephalic brain injury. Although the mechanism of this impairment is still speculative, these findings emphasize the importance of investigating the neuronal pathophysiology in hydrocephalus.