Browse

You are looking at 91 - 98 of 98 items for

  • Refine by Access: all x
  • By Author: Smyth, Matthew D. x
Clear All
Restricted access

Use of rapid-sequence magnetic resonance imaging for evaluation of hydrocephalus in children

William W. Ashley Jr., Robert C. McKinstry, Jeffrey R. Leonard, Matthew D. Smyth, Benjamin C. Lee, and Tae Sung Park

Object

The authors examine the use of rapid-sequence magnetic resonance (rsMR) imaging to make the diagnosis of malfunctioning and/or infected shunts in patients with hydrocephalus. Computerized tomography (CT) scanning is usually used in this context because it rapidly acquires high-quality images, yet it exposes pediatric patients to particularly high levels of radiation. Standard MR imaging requires longer image acquisition time, is associated with movement artifact, and, in children, usually requires sedation. Standard MR imaging provides greater structural resolution, yet visualization of ventricular catheters is relatively poor.

Methods

The authors analyzed a series of 67 rsMR imaging examinations performed without sedation in pediatric patients with hydrocephalus whose mean age was 4 years at the time of the examination. The mean study duration was 22 minutes. Catheter visualization was good or excellent in more than 75% of studies reviewed, and image quality was good or excellent in more than 60% of studies reviewed. The authors analyzed cancer risk with a model used for atomic bomb survivors. Fifty percent of their patients with hydrocephalus had undergone more than four brain imaging studies (CT or MR imaging) in their lifetimes. For the many patients who had undergone more than 15 studies, the total estimated lifetime attributable cancer mortality risk was calculated to be at least 0.35%.

Conclusions

Rapid-sequence MR imaging yields reliable visualization of the ventricular catheter and offers superior anatomical detail while limiting radiation exposure. The authors' protocol is rapid and each image is acquired separately; therefore, motion artifact is reduced and the need for sedation is eliminated. They recommend the use of rsMR imaging for nonemergent evaluation of pediatric hydrocephalus.

Restricted access

Magnetic resonance imaging evidence of posterior pharynx denervation in pediatric patients with Chiari I malformation and absent gag reflex

R. Shane Tubbs, Daniel Webb, Matthew D. Smyth, and W. Jerry Oakes

Object. The authors hypothesized that children with preoperative Chiari I malformation and an absent gag reflex may harbor pharyngeal musculature atrophy identifiable on magnetic resonance (MR) imaging.

Methods. Thirty patients with preoperative Chiari I malformation and a functioning gag reflex, five patients with preoperative Chiari I malformation and complete absence of gag reflex, and 50 control individuals underwent radiological measurement of the posterior pharyngeal wall thickness.

The thickness of the posterior pharyngeal wall in age-matched controls was significantly thinner (p < 0.0001) than that in patients with Chiari I malformation and no functioning gag reflex. Additionally, in patients with hindbrain herniation and absent gag reflex, the posterior pharyngeal wall thicknesses were comparable to or thinner than those in age-matched controls. A general decrease in the thickness of the posterior pharyngeal wall was found in control individuals who were older compared with patients with Chiari I malformation and a preserved gag reflex in whom the prevertebral soft tissues were found to increase in thickness with age.

Analysis of these data showed that in children with a nonfunctioning gag reflex the prevertebral soft tissue, composed primarily of the superior constrictor muscle, is statistically thinner compared with that in age-matched controls and age-matched children with Chiari I malformation and a functioning gag reflex. The authors theorize that the discrepancy between this measurement in controls and patients with hindbrain herniation is due to the thickening of the craniocervical ligaments that is known to occur in this clinical entity.

Conclusions. The finding that prevertebral soft tissue thickens with age in patients with Chiari I malformation and functioning gag reflex alone may aid in the interpretation of soft-tissue injury following cervical spine injuries in this group.

Restricted access

Arachnoid veils and the Chiari I malformation

R. Shane Tubbs, Matthew D. Smyth, John C. Wellons III, and W. Jerry Oakes

Object. The literature contains scant data regarding variations in anatomy at the level of the foramen of Magendie in patients with Chiari I malformation and syringomyelia.

Methods. Based on their operative experience and hospital data, the authors detailed the incidence of arachnoid veils found in juxtaposition to the foramen of Magendie in patients with hindbrain herniation. Additionally, radiological studies were retrospectively reviewed in cases in which such an anomaly was noted intraoperatively.

Of 140 patients with Chiari I malformation who underwent decompressive surgery, an associated syrinx was demonstrated in 80 (57%). The foramen of Magendie was obstructed by an arachnoid veil in 10 (12.5%) of these patients; once the lesion was punctured, the cerebrospinal fluid drained freely from this median aperture. On retrospective review of imaging studies, none of these anomalous structures was evident. In all patients with an arachnoid veil and syringomyelia resolution of syringomyelia was revealed on postoperative imaging.

Conclusions. In the absence of a clear pathophysiology of syrinx production, the authors would recommend that patients with syringomyelia and Chiari I malformation undergo duraplasty so that, if present, these veils can be fenestrated.

Restricted access

Efficacy of scheduled nonnarcotic analgesic medications in children after suboccipital craniectomy

Matthew D. Smyth, Jason T. Banks, R. Shane Tubbs, John C. Wellons III, and W. Jerry Oakes

Object. The authors performed a study to evaluate the efficacy of a regimen of scheduled minor analgesic medications in managing postoperative pain in children undergoing intracranial procedures.

Methods. Postoperative pain scores were analyzed in two groups of children who underwent decompressive surgery for Chiari malformation: Group A underwent a scheduled regimen of minor oral analgesic medications (standing doses of acetaminophen [10 mg/kg] and ibuprofen [10 mg/kg] alternating every 2 hours) and Group B received analgesic medication when requested.

Fifty children underwent a standard occipital craniectomy (25 in each group). The pain scores were significantly lower in Group A during most of the postoperative period. Length of stay (LOS) was shorter (2.2 compared with 2.8 days), and narcotic and antiemetic requirements were also lower in Group A patients than in Group B patients. Patients with spinal cord syringes exhibited a similar postoperative status to those without, and similar improvements in pain scores with scheduled minor analgesic medications were also evident.

Conclusions. A regimen of minor analgesic therapy, given in alternating doses every 2 hours immediately after craniotomy and throughout hospitalization, significantly reduced postoperative pain scores and LOS in children in whom suboccipital craniotomy was performed. Narcotic and antiemetic requirements were also decreased in association with this regimen. Application of this postoperative analgesia protocol may benefit children and adults in whom various similar neurosurgical procedures are required.

Restricted access

Complications of chronic vagus nerve stimulation for epilepsy in children

Matthew D. Smyth, R. Shane Tubbs, E. Martina Bebin, Paul A. Grabb, and Jeffrey P. Blount

Object. The aim of this study was to define better the incidence of surgical complications and untoward side effects of chronic vagus nerve stimulation (VNS) in a population of children with medically refractory epilepsy.

Methods. The authors retrospectively reviewed the cases of 74 consecutive patients (41 male and 33 female) 18 years of age or younger (mean age 8.8 years, range 11 months–18 years) who had undergone implantation of a vagal stimulator between 1998 and 2001 with a minimum follow up of 1 year (mean 2.2 years). Of the 74 patients treated, seven (9.4%) had a complication ultimately resulting in removal of the stimulator. The rate of deep infections necessitating device removal was 3.5% (three of 74 patients who had undergone 85 implantation and/or revision procedures). An additional three superficial infections occurred in patients in whom the stimulators were not removed: one was treated with superficial operative debridement and antibiotic agents and the other two with oral antibiotics only. Another four stimulators (5.4%) were removed because of the absence of clinical benefit and device intolerance. Two devices were revised because of lead fracture (2.7%). Among the cohort, 11 battery changes have been performed thus far, although none less than 33 months after initial implantation. Several patients experienced stimulation-induced symptoms (hoarseness, cough, drooling, outbursts of laughter, shoulder abduction, dysphagia, or urinary retention) that did not require device removal. Ipsilateral vocal cord paralysis was identified in one patient. One patient died of aspiration pneumonia more than 30 days after device implantation.

Conclusions. Vagus nerve stimulation remains a viable option for improving seizure control in difficult to treat pediatric patients with epilepsy. Surgical complications such as hardware failure (2.7%) or deep infection (3.5%) occurred, resulting in device removal or revision. Occasional stimulation-induced symptoms such as hoarseness, dysphagia, or torticollis may be expected (5.4%).

Restricted access

Atlantoaxial interlaminar distances in cervical flexion in children

R. Shane Tubbs, Matthew D. Smyth, John C. Wellons III, Jeffrey P. Blount, Paul A. Grabb, and W. Jerry Oakes

Object. To the best of the authors' knowledge, no quantitative analysis of the atlantoaxial interlaminar distance in flexion (ILD) in children exists in the medical literature. In this study they sought to determine the age-matched relationship between the posterior elements of the atlas and axis in children in cervical spine flexion, to be used as an adjunct to the atlantodental interval in common clinical use.

Methods. Lateral radiographs of the cervical spine in full flexion were analyzed in 74 children. The atlantoaxial ILD was defined as the distance between a midpoint of the anterior cortices of the atlantal and axial posterior arches.

The mean ILD for the entire group was 19 mm (range 8–30 mm). No significant difference was seen between male and female patients (p = 0.084). When stratified by age, the mean ILD was 12.3 ± 3 mm (15 cases) in children age 3 years or younger and 20.5 ± 4.7 mm (59 cases) in children age older than 3 years. Further stratification of the groups yielded a mean ILD of 10.4 ± 1.4 [eight cases]) in children age 1 to 2 years, and 14.4 ± 4.7 mm (seven cases) in children age 3 years. In children older than 3 years of age the mean ILD was consistently approximately 20 ± 5 mm regardless of age.

Conclusions. Rapid, safe, and accurate diagnosis of the cervical spine is essential in critical care. Knowledge of the distance between the posterior elements of the atlas and axis in flexion should enhance the clinicians' (those who clear cervical spines) ability to diagnose accurately atlantoaxial instability on lateral radiographs obtained in flexion.

Restricted access

Stereotactic radiosurgery for pediatric intracranial arteriovenous malformations: the University of California at San Francisco experience

Matthew D. Smyth, Penny K. Sneed, Samuel F. Ciricillo, Michael S. Edwards, William M. Wara, David A. Larson, Michael T. Lawton, Philip H. Gutin, and Michael W. Mcdermott

Object. Stereotactic radiosurgery for arteriovenous malformations (AVMs) is an accepted treatment option, but few reports have been published on the results of this treatment in children. In this study the authors describe a series of pediatric patients with a minimum follow-up duration of 36 months.

Methods. From 1991 to 1997, 40 children (26 boys and 14 girls) with AVMs were treated with radiosurgery at the University of California at San Francisco (UCSF). Follow-up information was available for 31 children (20 boys and 11 girls) in whom the median age at initial treatment was 11.2 years (range 3.4–17.5 years). The median follow-up duration was 60 months (range 6–99 months). Sixteen percent of the AVMs were Spetzler—Martin Grade II; 68%, Grade III; 10%, Grade IV; and 6%, Grade V. The mean volume of the AVMs was 5.37 cm3 and the median volume was 1.6 cm3. The mean marginal dose of radiation was 16.7 Gy and the median dose was 18 Gy (range 12–19 Gy).

Angiography performed in 26 children confirmed obliteration of the AVM nidus in nine patients (35%), partial response in 16 patients (62%), and no response in one patient (4%). In five patients who refused angiography, magnetic resonance (MR) imaging revealed obliteration in two patients and partial response in three patients, bringing the overall obliteration rate associated with initial radiosurgery to 35%. Logistic regression analysis confirmed a significant correlation between marginal dose prescription and response (p = 0.025); in AVMs that received at least 18 Gy there was a 10-fold increase in the obliteration rate (63%) over AVMs that received a lower dose. Lesions smaller than 3 cm3 were associated with a sixfold increased obliteration rate (53%) over lesions larger than 3 cm3 (8%), but AVM volume was not a statistically significant predictor of response (p = 0.09). Twelve patients have since undergone repeated radiosurgery and are currently being followed up with serial MR imaging studies (in five cases, the AVM is now obliterated). During the follow-up period (1918 patient-months) there were eight hemorrhages in five patients, with a cumulative posttreatment hemorrhage rate of 3.2%/patient/year in the 1st year and a rate of 4.3%/patient/year over the first 3 years. There were two permanent neurological complications (6%) and no deaths in this study.

Conclusions. The lower overall obliteration rate reported in this series is most likely due to the larger mean AVM volumes treated at UCSF as well as conservative dose—volume prescriptions delivered to children. Significantly higher obliteration rates were observed when a marginal radiation dose of at least 18 Gy was delivered. The permanent complication rate is low and should encourage those treating children to use doses similar to those used in adults.

Restricted access

Metastatic spinal ependymoma presenting as a vestibular schwannoma

Case illustration

Matthew D. Smyth, Lawrence Pitts, Robert K. Jackler, and Kenneth D. Aldape