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Dorothea Stiefel, Takashi Shibata, Martin Meuli, Patrick G. Duffy, and Andrew J. Copp

Object. Tethering of the spinal cord is a well-known complication in humans with spina bifida aperta or occulta. Its pathogenesis consists of a pathological fixation of the spinal cord resulting in traction on the neural tissue which, in turn, leads to ischemia and progressive neurological deterioration. Although well established in humans, this phenomenon has not been described in animal models of spina bifida.

Methods. A fetal mouse model with naturally occurring, genetically determined spina bifida was produced by generating double mutants between the curly tail and loop-tail mutant strains. Microdissection, labeling with 1,1′-dioctadecyl-3,3,3,′,3′-tetramethylindocarbocyanine perchlorate, immunohistochemistry for neurofilaments, H & E staining of histological sections, and whole-mount skeletal preparations were performed and comparisons made among mutant and normal fetuses.

Normal fetuses exhibited the onset of progressive physiological ascent of the spinal cord from embryonic Day 15.5. Spinal cord ascent resulted, by embryonic Day 18.5, in spinal nerve roots that pass caudolaterally from the spinal cord toward the periphery. In contrast, fetuses with spina bifida exhibited spinal cord tethering that resulted, at embryonic Day 18.5, in nerve roots that run in a craniolateral direction from the spinal cord. The region of closed spinal cord immediately cranial to the spina bifida lesion exhibited marked narrowing, late in gestation, suggesting that a potentially damaging stretch force is applied to the spinal cord by the tethered spina bifida lesion.

Conclusions. This mouse model provides an opportunity to study the onset and early sequelae of spinal cord tethering in spina bifida.

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Youichi Saitoh, Masahiko Shibata, Shun-ichiro Hirano, Masayuki Hirata, Takashi Mashimo, and Toshiki Yoshimine

✓ The authors tested a modified motor cortex stimulation protocol for treatment of central and peripheral types of deafferentation pain. Four patients with thalamic pain and four with peripheral deafferentation pain were studied. Preoperative pharmacological tests of pain relief were performed using phentolamine, lidocaine, ketamine, thiopental, and placebo. In five patients we placed a 20- or 40-electrode grid in the subdural space to determine the best stimulation point for pain relief for a few weeks before definitive placement of a four-electrode array. In three patients, the four-electrode array was implanted in the interhemispheric fissure as a one-stage procedure to treat lower-extremity pain. In two patients with pain extending from the extremity to the trunk or hip, dual devices were implanted to drive two electrodes.

Six of eight patients experienced pain reduction (two each with excellent, good, and fair relief) from motor cortex stimulation. No correlation was apparent between pharmacological test results and the effectiveness of motor cortex stimulation. Patients with peripheral deafferentation pain, including two with phantom-limb pain and two with brachial plexus injury, attained pain relief from motor cortex stimulation, with excellent results in two cases. Testing performed with a subdural multiple-electrode grid was helpful in locating the best stimulation point for pain relief. Motor cortex stimulation may be effective for treating peripheral as well as central deafferentation pain.

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Takehiro Uda, Ichiro Kuki, Takeshi Inoue, Noritsugu Kunihiro, Hiroharu Suzuki, Hiroshi Uda, Toshiyuki Kawashima, Kosuke Nakajo, Yoko Nakanishi, Shinsuke Maruyama, Takashi Shibata, Hiroshi Ogawa, Shin Okazaki, Hisashi Kawawaki, Kenji Ohata, Takeo Goto, and Hiroshi Otsubo

OBJECTIVE

Epileptic spasms (ESs) are classified as focal, generalized, or unknown onset ESs. The classification of ESs and surgery in patients without lesions apparent on MRI is challenging. Total corpus callosotomy (TCC) is a surgical option for diagnosis of the lateralization and possible treatment for ESs. This study investigated phase-amplitude coupling (PAC) of fast activity modulated by slow waves on scalp electroencephalography (EEG) to evaluate the strength of the modulation index (MI) before and after disconnection surgery in children with intractable nonlesional ESs. The authors hypothesize that a decreased MI due to surgery correlates with good seizure outcomes.

METHODS

The authors studied 10 children with ESs without lesions on MRI who underwent disconnection surgeries. Scalp EEG was obtained before and after surgery. The authors collected 20 epochs of 3 minutes each during non–rapid eye movement sleep. The MI of the gamma (30–70 Hz) amplitude and delta (0.5–4 Hz) phase was obtained in each electrode. MIs for each electrode were averaged in 4 brain areas (left/right, anterior/posterior quadrants) and evaluated to determine the correlation with seizure outcomes.

RESULTS

The median age at first surgery was 2.3 years (range 10 months–9.1 years). Two patients with focal onset ESs underwent anterior quadrant disconnection (AQD). TCC alone was performed in 5 patients with generalized or unknown onset ESs. Two patients achieved seizure freedom. Three patients had residual generalized onset ESs. Disconnection surgeries in addition to TCC consisted of TCC + posterior quadrant disconnection (PQD) (1 patient); TCC + AQD + PQD (1 patient); and TCC + AQD + hemispherotomy (1 patient). Seven patients became seizure free with a mean follow-up period of 28 months (range 5–54 months). After TCC, MIs in 4 quadrants were significantly lower in the 2 seizure-free patients than in the 6 patients with residual ESs (p < 0.001). After all 15 disconnection surgeries in 10 patients, MIs in the 13 target quadrants for each disconnection surgery that resulted in freedom from seizures were significantly lower than in the 26 target quadrants in patients with residual ESs (p < 0.001).

CONCLUSIONS

In children with nonlesional ESs, PAC for scalp EEG before and after disconnection surgery may be a surrogate marker for control of ESs. The MI may indicate epileptogenic neuronal modulation of the interhemispheric corpus callosum and intrahemispheric subcortical network for ESs. TCC may be a therapeutic option to disconnect the interhemispheric modulation of epileptic networks.