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Michael G. Muhonen, Arnold H. Menezes, Paul D. Sawin and Stuart L. Weinstein

✓ A prospective study was undertaken in 1985 to better understand how the surgical manipulation of hind-brain herniation affected abnormal spinal curvature. Eleven patients under 16 years of age with Chiari malformation (not associated with myelodysplasia) and scoliosis of at least 15° were studied. The mean curve angle at the time of original treatment was 29°, with the convexity to the right in seven patients. The curvature was rapidly progressing in four patients. The most common presenting signs were myelopathy and weakness. Investigative procedures included spine radiographs with the patient standing and magnetic resonance (MR) imaging of the brain, spinal cord, and craniovertebral junction. Eight children had associated hydrosyringomyelia.

Surgical intervention consisted of a dorsal posterior fossa decompression in all patients and a transoral ventral decompression of the cervicomedullary junction in five. All patients were followed at 3, 6, and 12 months, and at yearly intervals thereafter with clinical evaluations, spine radiographs in the standing position, and postoperative MR imaging. The mean follow-up period was 35 months. The scoliosis improved in eight patients, stabilized in one, and progressed in two. Only one child required postoperative spinal fusion and instrumentation for progression of scoliosis. Hematomyelia or hematobulbia was associated with persistent scoliosis in two patients. The presence of hydrosyringomyelia and bone erosion did not preclude curve improvement. All patients under 10 years of age had resolution of their scoliosis, despite preoperative curves of more than 40°. These findings emphasize the importance of early surgical intervention, with the restoration of normal cerebrospinal fluid dynamics at the craniovertebral junction in children with symptomatic Chiari malformations.

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Paul D. Sawin, Michael G. Muhonen and Arnold H. Menezes

✓ The etiology of occipital plagiocephaly (OP) is not fully understood. The authors have observed that many infants with this condition have external hydrocephalus. This study was undertaken to quantify cerebrospinal fluid (CSF) space caliber in children with OP and to compare these measurements to those derived from normal age-matched controls to further elucidate the pathogenesis of this condition.

Thirty-one infants with isolated unilateral OP (mean age 6 months) were studied. Infants with multiple cranial suture abnormalities, impaired neurological function, developmental delay, and associated craniofacial anomalies were excluded. Twenty normal infants were evaluated as controls. The volumes of the sylvian fissures, frontal and occipital subarachnoid spaces, as well as the cross-sectional areas of the suprasellar and perimesencephalic cisterns, were calculated from computerized tomography (CT) studies. Ventricular size was also assessed.

Generalized subarachnoid space dilation was observed in 29 (93.5%) of the 31 children with OP. Head circumference was significantly greater in the case group (71.4 vs. 50.8 percentile; p = 0.0002 by analysis of variance). The sylvian fissure volume was significantly larger in the case group (5.8 ml vs. 0.7 ml in controls, p < 0.0001). The volume of the contralateral sylvian fissure was greater than that ipsilateral to the side of OP (7.1 ml vs. 4.5 ml, p = 0.001). Frontal subarachnoid space volume was greater in infants with OP (27.5 ml vs. 0.6 ml in controls, p < 0.0001). Both the suprasellar and perimesencephalic cisterns were of greater caliber in the case group (p = 0.007 and p < 0.0001, respectively). No difference in ventricular size or occipital subarachnoid space volume was noted between groups.

The extraventricular CSF spaces in neurologically unimpaired infants with OP are significantly larger than those in age-and sex-matched controls. Enlarged subarachnoid spaces may increase the compliance and malleability of the calvaria and sutures, predisposing to positional deformity. External hydrocephalus may be a fundamental etiological factor in OP.

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Michael G. Muhonen, Scott C. Robertson, Jeffrey S. Gerdes and Christopher M. Loftus

✓ Serotonin (5-HT) produces constriction of peripheral collateral blood vessels. Using an animal model, the authors tested the hypothesis that 5-HT constricts collateral vessels in the cerebrum. A branch of the middle cerebral artery (MCA) was occluded proximally and cannulated distally in anesthetized dogs. Blood flow to the area at risk for infarction was detected by perfusing the cannulated MCA branch with microsphere-free blood during systemic injection of radioactive microspheres (shadow flow technique). Blood flow to collateral-dependent and normal cerebrum was measured during intravenous infusion of 5-HT (10 and 40 mg/kg/minute). Serotonin produced a dose-related reduction of blood flow to collateral-dependent cerebrum, increased collateral vessel resistance in large cerebral arteries and collateral vessels, and decreased cerebral artery perfusion pressure. In contrast, blood flow to normal cerebrum was not altered because a decrease in small vessel resistance effectively compensated for a decrease in MCA perfusion pressure. These findings indicate that 5-HT produces constriction of collateral vessels in the cerebrum. This response is clearly different from normal small cerebral vessels, which dilate during 5-HT infusion.

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Michael G. Muhonen, Jeremy S. Bierman, Namath S. Hussain, Heather A. Hanley and Sara S. Hussain

✓Antenatal diagnosis of an intracranial neoplasm is extremely rare. The authors describe a case in which a 21-week-old fetus was found, by using fetal ultrasonography, to have a large intracranial mass. Fetal magnetic resonance (MR) images, obtained at 21 and 25 weeks' gestation, supported the diagnosis of a teratoma. As the tumor increased in size, near-complete brain atrophy ensued. Premature labor was induced, and a nonviable fetus died within minutes of delivery. Post-mortem analysis confirmed a teratoma occupying a major portion of the intracranial space. In cases in which abnormal brain development is suspected in a fetus, the use of fetal MR imaging can give a clearer picture of the pathological entity, which may allow for a more accurate diagnosis. The usefulness of fetal MR imaging in monitoring brain development and tumor growth during treatment planning is discussed.

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Charles A. Middelhof, William G. Loudon, Michael D. Muhonen, Christopher Xavier and Clarence S. Greene Jr.

✓Central nervous system (CNS) aspergillosis remains a daunting diagnosis. This opportunistic mycosis historically carries a mortality rate approaching 100% in immunocompromised patients, with death ensuing within days after the onset of neurological symptoms. From their literature review, the authors concluded that children contracting CNS aspergillosis while undergoing systemic chemotherapy for leukemias represent a particularly unfortunate prognostic group. Antifungal medications prove ineffective for treating CNS aspergillosis in patients immunocompromised because of their chemotherapy regimens. In contrast, withholding chemotherapy to reverse immunosuppression, thereby improving the efficacy of antifungal medications, allows for progression of the primary leukemic disease. The authors present a series of four immunosuppressed patients whose course of treatment for leukemia was complicated by CNS Aspergillus sp. abscesses. Multiple cerebral fungal abscesses developed in two patients and a single cerebral abscess developed in two. All four patients underwent frameless stereotactic resection of the aspergilloma. All children later experienced resolution of their CNS infections and full neurological recovery. At 2- to 4-year follow ups, one patient has died of leukemia and the other three continue to thrive without evidence of recurrent aspergillosis. Given the grave natural history cited in the literature for this disease when medical treatment is instituted alone, the authors stress the crucial role of stereotactic neurosurgery for the intelligent treatment of immunocompromised children suspected of harboring a CNS aspergilloma abscesses. The authors propose that the goal for successful treatment in these patients should be gross-total resection of the abscess, its wall, and its capsule.

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Franklin D. Westhout, Michael G. Muhonen and Chiedozie I. Nwagwu

✓ The authors report a case of short-term high-dose propofol-related metabolic acidosis in a 3-year-old girl. The patient initially presented at another institution with left fourth cranial nerve palsy, and examination revealed a large, wide-necked 19 × 22 × 17–mm aneurysm in the left internal carotid artery. She had undergone three previous unsuccessful attempts at endovascular coil embolization, which were complicated by repeated coil protrusions into the parent vessel.

During angiography and a balloon occlusion test (BOT) 80 mg propofol was given for 3 hours followed by 200 μg/kg/min for another 4 hours. The 20-minute BOT was well tolerated, and the aneurysm was occluded with stent-assisted coil embolization.

Following the procedure the patient developed severe acidosis, hypotension, tachycardia, and signs of cardiac failure. On postoperative Day 3 her metabolic acidosis resolved, and she was weaned off sedatives. She continued to improve and was discharged from the hospital on postoperative Day 7. The metabolic acidosis and hypotension were thought to be due to propofol-related infusion syndrome.

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Marlon S. Mathews, William G. Loudon, Michael G. Muhonen and Michael J. Sundine

✓Due to early diagnosis and treatment of hydrocephalus, neurosurgeons rarely are called upon to treat patients with extreme hydrocephalic macrocephaly. Macrocephaly can limit mobility and hygiene. The critical evaluation and surgical correction of the morphological problem of macrocephaly secondary to hydrocephalus is complex. Various techniques such as quadrantal, picket fence, crossbar, and modified π techniques have been used to reduce the size of the cranial vault to decrease cranial volume while achieving good cosmesis. Limitations of vault reduction cranioplasty include the inability to alter the anteroposterior and lateral diameters of the skull base, the inability to shorten the superior sagittal sinus, and the need to avoid infolding of the brain due to the risk of venous infarcts. Reduction cranioplasty is indicated in the occasional patient whose large head size represents a mechanical or cosmetic problem of sufficient magnitude to seriously interfere with motor development and functioning, with resultant development of pressure sores and difficulties with nursing care. Reduction cranioplasty should be avoided in patients under the age of 3 years.

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Daniel S. Yanni, Aurora S. Cruz, Alexander Y. Halim, Amandip S. Gill, Michael G. Muhonen, Robert F. Heary and Ira M. Goldstein

Pediatric spinal trauma can present a surgeon with difficult management decisions given the rarity of these cases, pediatric anatomy, and a growing spine. The need to stabilize a traumatically unstable pediatric spine can be an operative challenge given the lack of instrumentation available. The authors present a surgical technique and an illustrative case that may offer a novel, less disruptive method of stabilization. A 2-year-old girl presented after an assault with an L1–2 fracture subluxation with lateral listhesis and fractured jumped facets exhibited on CT scans. CT also showed intact growth plates at the vertebral body, pedicles, and posterior elements. MRI showed severe ligamentous injury, conus medullaris compression, and an epidural hematoma. Neurologically, the patient moved both lower extremities asymmetrically. Given the severity of the deformity and neurological examination and disruption of the stabilizing structures, the authors made the decision to surgically decompress the L-1 and L-2 segments with bilateral laminotomies, evacuate the epidural hematoma, and reduce the deformity with sublaminar stabilization using braided polyester cables bilaterally, thus preserving the growth plates. They also performed a posterolateral onlay fusion at L-1 and L-2 using autograft and allograft placed due to the facet disruption. At the 42-month follow-up, imaging showed fusion of L-1 and L-2 with good alignment, and the hardware was subsequently explanted. The patient was neurologically symmetric in strength, ambulating, and had preserved alignment. Her bones and spinal canal continued to grow in relation to the other levels.