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Jeffrey P. Blount and Scott Elton

Lipomas of the spinal cord are among the most fascinating lesions encountered by the pediatric neurosurgeon. An understanding of spinal lipomas may, however, be difficult because the terminology used to describe the accumulations of spinal fat is confusing, inconsistently applied, and at times contradictory. An anatomical characterization of lipomas may assist in understanding these lesions. Lipomas of the spinal cord are very rare and cause symptoms related to mass effect and secondary compressive myelopathy. Lipomas of the conus medullaris (or lipomyelomeningocele) are the most common form of fatty masses in the spine and can be divided into dorsal, caudal, and transitional forms. These lesions are a manifestation of occult spinal dysraphism and a common cause of the tethered cord syndrome (TCS). The natural history of untreated lipomyelomeningocele, although incompletely understood, appears to be progressive neurological deterioration with loss of bladder control. Timely, careful surgical intervention may prevent significant neurological deterioration and progressive disability in the majority of children harboring these lesions. In surgical intervention the surgeon seeks to disrupt the connection between the fibrofatty mass and underlying cord as well as to reestablish normal anatomical planes. Several intraoperative video segments illustrating lipomyelome-ningocele resection are included in this paper. Lipomas of the terminal filum (fatty filum) are truly occult and are also associated with TCS. Surgical treatment of filum lipomas carries significantly lower risk than that for lipomas of the conus medullaris. Again, the goal of surgery is to disrupt the connection between the abnormal fibrofatty tissue and the underlying spinal cord.

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Jeffrey P. Blount, W. Jerry Oakes, R. Shane Tubbs and Robin P. Humphreys

✓ Vein of Galen aneurysmal malformations are a mixed group of lesions characterized by an abnormal fistula between abnormal distal branches of the choroidal and/or posterior cerebral arteries and the great vein of Galen. In this paper the authors trace the historical evolution of the current approach to diagnosis and treatment, and the literature is reviewed comprehensively. During the historical era, vein of Galen malformations were described in individual case reports and an early classification system was developed. In the early era of treatment, open surgery was the preferred approach, although morbidity and mortality rates were high. The development of neurointerventional techniques allowed the introduction of occlusive materials into the fistula, with pronounced improvements in clinical outcome.

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Jeffrey P. Blount, R. Shane Tubbs, W. Jerry Oakes and Robin P. Humphreys

✓ Arteriovenous malformations (AVMs) are the most common cause of intracerebral hemorrhage in children. In this paper the authors trace the historical evolution of the recognition, diagnosis, and treatment of pediatric intracerebral AVMs, and they summarize the contemporary approach and current controversies surrounding treatment of these lesions. Important distinctions between adult and pediatric AVMs are emphasized.

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Jeffrey P. Blount, W. Jerry Oakes, R. Shane Tubbs and Robin P. Humphreys

✓ Intracranial aneurysms are rare in children, and their origins and treatment methods tend to be different from those in these same entities in adults. These lesions tend to be congenital or to have an infectious or traumatic origin. In the current paper the authors trace the historical evolution of the diagnosis and treatment of intracranial aneurysms in children. Based on the literature, these lesions appear to occur in children in less than 3% of all series. The literature also supports the suggestion that symptoms from these aneurysms are often from mass effect and that giant aneurysms and lesions in the posterior cranial fossa are relatively more common in children than in adults. The termination of the carotid artery and the anterior cerebral artery seem to be disproportionately common sites of aneurysm formation in this cohort. Interestingly, surgical outcomes in children appear to be moderately better than in adults. Based on the literature, the claim can be made that a multidisciplinary approach to the management of such aneurysms can yield good outcomes in a very high percentage of children treated.

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R. Shane Tubbs, E. George Salter, John C. Wellons III, Jeffrey P. Blount and W. Jerry Oakes

Object

There is a paucity of information in the neurosurgical literature regarding the surgical anatomy surrounding the posterior interosseous nerve (PIN). The goal of the current study was to provide easily recognizable superficial bone landmarks for identification of the PIN.

Methods

Thirty-four cadaveric upper extremities obtained from adults were subjected to dissection of the PINs, and measurements were made between this nerve and surrounding superficial bone landmarks.

In all specimens the main radial trunk was found to branch into its superficial branch and PIN at the level of the lateral epicondyle of the humerus. Proximally, the PIN was best identified following dissection between the brachioradialis and extensor carpi radialis longus and brevis muscles. At its exit site from the supinator muscle, the PIN was best identified after retraction between the extensor carpi radialis longus and brevis and extensor digitorum communis muscles. This site was a mean distance of 6 cm distal to the lateral epicondyle of the humerus. No compression of the PIN by the tendon of origin of the extensor carpi radialis brevis muscle was seen. One specimen was found to have a proximally split PIN that provided a previously undefined articular branch to the elbow joint. The mean diameter of the PIN proximal to the supinator muscle was 4.5 mm. The leash of Henry crossed the PIN in all but one specimen and was found at a mean distance of 5 cm inferior to the lateral epicondyle. The PIN exited the distal edge of the supinator muscle at a mean distance of 12 cm distal to the lateral epicondyle of the humerus. Here the mean diameter of the PIN was 4 mm. The exit site from the distal edge of the supinator was found to be at a mean distance of 18 cm proximal to the styloid process of the ulna. This exit site for the PIN was best identified following dissection between the extensor carpi radialis longus and brevis and extensor digitorum communis muscles. The distal articular branch of the PIN was found to have a mean length of 13 cm and the proximal portion of this terminal segment was located at a mean distance of 7.5 cm proximal to the Lister tubercle.

Conclusions

The addition of more anatomical landmarks can help the neurosurgeon to be more precise in identifying the PIN and in avoiding complications during surgery in this region.

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Hyunmi Kim, Catherine Lee, Robert Knowlton, Curtis Rozzelle and Jeffrey P. Blount

Object

Depth electrodes provide a better sampling of sulci and regions of cortex that lie tangential to the plane of subdural electrodes. The aim of this study was to evaluate the utility of supplemental depth electrodes in the surgical treatment of pediatric patients with neocortical epilepsy.

Methods

Cases involving 12 consecutive pediatric patients (mean age [SD] 10.9 ± 4.4 years) were reviewed. Focal resective surgery (in 9 cases) or functional hemispherectomy (in 3 cases) was performed after intracranial monitoring. The mean total number of electrodes was 118 ± 29; the mean numbers of grid, strip, and depth electrodes were 95 ± 27, 10 ± 6, and 13 ± 5, respectively The most common pathological condition was focal cortical dysplasia.

Results

In 4 cases, depth electrodes demonstrated the ictal onset zone in an area not easily accessible by grids or strips (in the basal temporal region in 3 cases and the upper opercular region in 1 case). In 3 of these 4 cases, the ictal onset zone was defined exclusively by the depth electrodes. In each of these 3 cases, the surface electrodes (on grids or strips) demonstrated early propagation but not ictal onset. In 9 cases, the depth electrodes also demonstrated the early propagation zone. The information about the ictal onset zone and the early propagation zone helped to provide additional information that affected the extent (in 7 cases) or depth (in 3 cases) of the resection. The proportion of the electrodes involved in resection relative to the total number of implanted electrodes was low (mean ± SD, 0.26 ± 0.09). Nine patients (75.0%) became seizure free (Engel class IA outcome) after surgery (mean duration of follow-up 25.7 ± 4.29 months). There were no surgical complications related to intracranial electroencephalography monitoring.

Conclusions

Most patients (75.0%) became seizure free after extensive monitoring and more limited resection of seizure-onset regions. Supplemental depth electrodes contribute to improved outcome by providing information about the ictal onset zone that is not accessible by grid or strip electrodes in some cases. The supplemental depth electrodes conferred an extra dimension of depth to the analysis, which allowed for successful outcome with more limited resection.

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Jeffrey P. Blount, Amber S. Gordon, Paul M. Foreman and John H. Grant

The authors report on an infant with a bifrontal encephalocele that was associated with multisuture craniosynostosis, spasticity, and a progressively severe epilepsy. They describe the initial presentation, genetic screening results, staged multidisciplinary operative plans, clinical course, complications, and long-term surgical and developmental follow-up. To their knowledge, the comprehensive surgical management of this type of complicated congenital cranial anomaly has not been previously described.

Surgical management was staged and multidisciplinary and required careful attention to all 3 components of the condition: 1) hydrocephalus, 2) frontal meningoencephalocele, and 3) epilepsy.

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Daxa M. Patel, R. Shane Tubbs, Gigi Pate, James M. Johnston Jr. and Jeffrey P. Blount

Object

Surveillance imaging of the cerebral ventricles can be valuable in following up children with shunt-treated hydrocephalus. There also, however, has been recent increased awareness and concern over the potential risk associated with imaging-related radiation exposure in children. Magnetic resonance imaging represents an imaging alternative that does not use ionizing radiation; however, its practical utility has been limited due to the near-uniform requirement for sedation or general anesthesia in children. Magnetic resonance imaging without sedation is often futile because of the movement artifact produced by the nonsedated pediatric patient. Some studies have demonstrated the feasibility of using fast-sequence MRI (fsMRI), but the reported experiences are limited. The authors have incorporated fsMRI into their routine shunt surveillance imaging paradigms and report here a 5-year experience with this modality.

Methods

The authors initially started using fsMRI for routine surveillance in a single clinic in 2008 and have gradually increased their institutional utilization of this modality as experience has accumulated and protocols have been refined. Imaging sequences obtained for each child include an axial T2-weighted half-Fourier acquisition single-shot turbo spin-echo (HASTE), coronal T2-weighted HASTE, and sagittal T2-weighted HASTE images. The authors conducted a retrospective chart and imaging review. They rated each fsMR image according to 5 visibility parameters: 1) ventricle size, 2) ventricle configuration, 3) presence or absence of transependymal flow, 4) presence or absence of motion artifact, and 5) visualization of the ventricular catheter. Each parameter was graded as 1 (present) or 0 (absent). Thus, the maximum value assigned to each scan could be 5 and the minimum value assigned to each scan could be 0. Interrater reliability between pairs of observers was calculated using the Kendall's tau-b and intraclass coefficients.

Results

Two hundred patients underwent fsMRI. No child required sedation. The average duration of examinations was approximately 3.37 minutes, and mean age of the patients was 5.7 years. Clinically useful images were attained in all cases. Overall quality of the fsMRI studies based on the 5 different visibility parameters showed that 169 images (84.5%) included 4 or 5 parameters (score ≥ 4) and had statistically significant excellent quality. The Kendall's tau-b for the overall fsMRI ratings was 0.82 (p = 0.002) and the intraclass coefficient was 0.87 (p < 0.0001).

Conclusions

In the present cohort of 200 patients, fsMRI studies were shown to have an excellent overall quality and a statistically significant high degree of interrater reliability. Consequently, the authors propose that fsMRI is a sufficiently effective modality that eliminates the need for sedation and the use of ionizing radiation and that it should supplant CT for routine surveillance imaging in hydrocephalic patients.

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Jeffrey P. Blount, Kent B. Remley, Samuel K. Yue and Donald L. Erickson

✓ Intrathecal morphine delivered by implanted pumps has been used in the treatment of pain caused by terminal cancer. Some authors supports its use in benign pain as well. The authors present three cases in which chronic infiltration of intraspinal narcotic medication was complicated by the formation of a granulomatous mass that became large enough to exert mass effect and induce neurological dysfunction.