Edward R. Smith and R. Michael Scott
Moyamoya is a progressive arteriopathy of unknown origin affecting the branches of the internal carotid artery (ICA). The arteriopathy can present as an isolated medical condition, affecting both sides of the brain (“moyamoya disease”) or can be unilateral or found in association with systemic disorders (“moyamoya syndrome”). The ischemia resulting from luminal narrowing predisposes children to transient ischemic attacks and stroke—the primary presentations of affected patients. Although it is rare—affecting 1 in 1 million children in the US—moyamoya is implicated in 6% of all childhood strokes. Diagnosis is defined by characteristic findings on arteriograms, including stenosis of the branches of the ICA and a pathognomonic spray of small collateral vessels in this region, descriptively likened to a “puff of smoke” (“moyamoya” in Japanese). Treatment is predicated on restoration of cerebral blood flow by surgical revascularization. The rarity of this disorder has limited research and the development of evidence-based clinical management. While acknowledging these limitations, in this article the authors aim to summarize current studies of pediatric moyamoya, with the objective of providing a framework for construction of evidence-based guidelines for treatment. The compilation of current data in these guidelines should serve as a resource to aid pediatric neurosurgeons in their role as advocates for providing appropriate care to affected children.
R. Michael Scott and Edward R. Smith
This issue of Neurosurgical Focus is devoted to the topic of moyamoya disease/syndrome. When the senior editor (R.M.S.) was a neurosurgical resident in the late 1960s and early 1970s, the condition was virtually unknown in the Western hemisphere, and patients with “cerebrovascular insufficiency” and the typical arterial findings on angiography were believed to have a type of arteritis. The refinement of catheter angiography techniques and the development of the imaging modalities of CT and MR imaging clarified the significance of making the correct diagnosis of moyamoya disease in affected patients, and with the development of direct and then indirect revascularization procedures during this same period, neurosurgeons became involved in the disease's treatment.
Edward R. Smith and R. Michael Scott
Progression of vasculopathy associated with moyamoya syndrome is extremely variable. The authors review their experience in patients with unilateral moyamoya syndrome to identify factors predictive of contralateral clinical and imaging-documented disease progression.
The authors reviewed the clinical and imaging records of all patients with moyamoya syndrome and unilateral disease who underwent cerebral revascularization surgery between January 1985 and June 2006 by using a standardized surgical procedure, pial synangiosis.
Of 235 surgically treated patients with moyamoya syndrome, 33 (14%) presented with unilateral disease (4 adults and 29 children). There were 16 female and 17 male patients, with an average age of 10.4 years (26.8 years for adults and 8.1 years for children; range 1.5–39 years). Twenty patients presented with left-sided disease and 13 with right-sided disease.
The average follow-up after surgery was 5.3 years (3.1 years for adults and 5.6 years for children; range 1–16 years). During this period, 10 (30%) of 33 patients progressed to bilateral disease. The mean time until disease progression was 2.2 years (range 0.5–8.5 years). Factors associated with progression in this series included contralateral abnormalities on initial angiography, previous history of congenital cardiac anomaly, cranial irradiation, Asian ancestry, and familial moyamoya syndrome. Young age at diagnosis was associated with a more rapid rate of progression (age < 7 years, 0.9 years to progression and age ≥ 7 years, 3.1 years to progression).
Of patients with unilateral moyamoya syndrome, 30% will have progression of arteriopathy during long-term follow-up. In this series, the average time of progression from unilateral to bilateral angiographic disease was 2.2 years. Several factors, including contralateral abnormalities on initial imaging, congenital cardiac anomaly, previous cranial irradiation, Asian ancestry, and familial moyamoya syndrome, were associated with an increased risk of progression. Patients with known unilateral angiographic disease should undergo continued monitoring by using MR imaging and MR angiography at regular intervals. Treatment with pial synangiosis is safe and confers durable protection against stroke in patients with both bilateral and unilateral moyamoya syndrome.
Joseph R. Madsen and R. Michael Scott
Mark R. Proctor and R. Michael Scott
Split cord malformations (SCMs) are relatively rare forms of occult spinal dysraphism (OSD) and tethered spinal cord syndrome. The majority of these cases present in early childhood, with neurocutaneous stigmata being an early presenting feature. Prophylactic detethering surgery is advocated by most neurosurgeons due to the risk of neurological deterioration over time caused by patient growth and activity. However, unlike other forms of OSD, the course of SCM progression after surgery is not well understood, and little has been published about long-term follow-up results. In this study the authors review the results obtained in 16 patients in whom the senior author performed surgery over a 13-year period (average length of follow up almost 8 years).
Presentation, surgical approach, and outcome are evaluated, and the long-term outcome of neurological status, pain, bowel/bladder disturbance, and spinal deformities are emphasized.
The primary conclusion is that patients with SCM generally tolerate surgery well and experience few complications. Neurological deterioration is rare except in cases in which retethering occurs, (two patients in this series). Although impaired bowel and bladder function was stabilized or improved and pain was reliably relieved postoperatively, preexisting vertebral column deformities usually progressed after surgery and, in most cases, required spinal fusion.
Coleman P. Riordan and R. Michael Scott
In patients with syringomyelia and type I Chiari malformation (CM-I) who have required reoperation because of persistent, recurrent, or expanding syrinx, the senior author placed a stent from the fourth ventricle to the cervical subarachnoid space in hopes of promoting circulation of CSF out of the ventricle and away from the central canal of the spinal cord. This study was undertaken to determine the long-term success of this operative stratagem in eliminating the syrinx, as well as to document the complications that occurred following stent placement. The technique utilized for placement of fourth ventricle stents is presented.
The surgical database of the senior author was reviewed to identify all patients who underwent stent placement at a reexploration of a suboccipital decompression for a CM-I conducted for a recurrent or ineffectively treated syringomyelia. The clinical and radiological data of these patients were analyzed to determine long-term efficacy and complications of the procedure.
Fourteen patients (average age 10.7 ± 5.2 years, range 2.6–20.1 years) were identified who met these inclusion criteria. They each presented with recurrent, residual, or expanding syringomyelia following a prior decompression for a CM-I. The reoperation with stent placement was complicated by late stent dislodgement and recurrence or persistence of the syrinx in 2 patients (14%) and by neurological deficit in 1 patient (7%). There was 1 perioperative CSF leak (7%). In 1 other patient (7%), the stent dislodged after surgery but required no further intervention, as the syrinx remained collapsed. Two patients (14%) required late reoperation for stent replacement when syrinxes recurred. At the most recent imaging follow-up, the stent was positioned appropriately in 12 patients (86%; average follow-up 6.9 years, range 0.5–18.1 years), and the recurrent or residual syrinx was eliminated or reduced in size by 75% or greater in 13 patients (93%).
The placement of a stent from the fourth ventricle to the cervical subarachnoid space was a highly effective treatment for patients with recurrent, residual, or expanding syringomyelia following an initial decompression of an associated CM-I. The sole neurological complication in this series was related to lysis of arachnoid scar rather than stent placement itself, but inability to maintain fixation of the stent in situ led to further surgery to replace the stent in 2 patients.
Marc S. Schwartz and R. Michael Scott
The authors report the case of a 30-year-old woman who was a long-term intranasal cocaine abuser and who presented with transient ischemic attacks and multiple cerebral infarctions that were associated with moyamoya syndrome. The authors suggest that, because of its sympathomimetic effects, chronic cocaine use may promote intracranial arterial stenosis, distal ischemia, and subsequent formation of moyamoya-like vessels. The patient has remained clinically stable with no new episodes of stroke 6 years after undergoing “pial synangiosis” (modified encephaloduroarteriosynangiosis) to revascularize both hemispheres. Cocaine abuse may lead to moyamoya syndrome and may represent a chronic effect on the cerebral vasculature.
Cormac O. Maher and R. Michael Scott
The authors reviewed the experience of a single surgeon in the surgical treatment of arteriovenous malformations (AVMs) in children, with specific attention to the angioarchitectural appearance of these lesions.
The authors performed a retrospective review of pediatric cases of AVM treated at a single institution over a 15-year period. Inclusion criteria consisted of pediatric age at time of treatment and resection of a pial AVM. The AVMs were considered linear-based if they had a single, centrally located, dominant vein with a linear configuration rather than the typical central nidus.
Sixty-seven patients, ranging in age from 6 months to 17 years, underwent surgical treatment of an AVM between January 1, 1990, and December 30, 2005. In these patients, 31 AVMs (46%) had a distinct linear configuration that was centered on a dominant draining vein (“vein-based”). These AVMs presented with hemorrhage (61%), incidental findings on imaging (16%), or seizures (13%). In 4 cases, AVM recurrence was noted on angiographic follow-up after postoperative angiography showed no residual lesion. Recurrence was seen at 1 year in 2 cases, and at 3 and 11 years in 1 case each.
A linear vein–based morphological pattern is common in pediatric AVMs and may recapitulate the embryological origins of the cerebral circulation. Surgical treatment in these cases can also be vein-based, through a narrow surgical corridor, which leads to minimal cortical disruption.