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Matthew D Smyth

Publications and source records attributed to Matthew D Smyth.

35 records · Page 2Linked to original sources
PubMed2003

Life expectancy of ventriculosubgaleal shunt revisions.

The subgaleal shunt has been and is currently used for the temporary bypass of the normal cerebrospinal fluid (CSF) pathways. We retrospectively reviewed all subgaleal shunts placed at the Children's Hospital, Birmingham, Ala., USA, from 1993 to the present and examined the life expectancy of revisions of this temporary method of CSF diversion. The average length of survival of primary, secondary and tertiary subgaleal shunts in this population was 37.4, 32.4 and 19.6 days, respectively. This current review demonstrates that the majority of patients in whom a subgaleal shunt is utilized may continue to obtain therapeutic diversion of their CSF for greater than 2.5 months with intermittent subgaleal shunt revisions. In the majority of cases, this length of time is sufficient to manage and resolve issues that would make ventriculoperitoneal shunting undesirable.

Adolescent↗
PubMed2003

Children with growth hormone deficiency and Chiari I malformation: a morphometric analysis of the posterior cranial fossa.

OBJECTIVE: The posterior fossa (PF) has been found to be small in various forms of Chiari malformation. Explanations involving a connection between growth hormone deficiency (GHD) and Chiari I malformation (CIM) have been proposed. However, to date, no quantitative analysis of the PF of patients with CIM and GHD has been performed. Our study was performed to determine the geometry of the PF in children with GHD and CIM. METHODS: Morphometric analysis of the PF was performed in 10 children with GHD and CIM (group 1), 20 children with GHD and no CIM (group 2) and 50 controls. RESULTS: PF volumes for group 1 ranged from 128 to 259 +/- 33 ml, and for group 2, they ranged from 115 to 186.2 +/- 25.4 ml. Lengths of the foramen magnum for groups 1 and 2 had means of 36 and 38 mm, respectively. The mean basiocciput length and tentorial angle for groups 1 and 2 were 20 and 19 mm and 89 and 87.5 degrees, respectively. CONCLUSIONS: We have determined that children with GHD with or without CIM have no significant difference in their PF volume compared to controls. However, our data demonstrate significant underdevelopment of portions of the bony PF in both patients with GHD alone and in patients with GHD and CIM. Tentorial angles were elevated in noncontrol groups. We propose that this association is not due to an increased rate of 'midline' defects seen in GHD but rather a structurally distorted PF that is not capacious enough to house the entire developing rhombencephalon. These data will hopefully aid in the further understanding of the pathophysiology of CIM.

Adolescent↗
PubMed2003

Alternative uses for the subgaleal shunt in pediatric neurosurgery.

The subgaleal shunt has been used for the temporary bypass of the normal cerebrospinal fluid (CSF) pathways. We retrospectively reviewed all subgaleal shunts placed at the Children's Hospital, Birmingham, Ala., USA, from 1997 to the present and examined all uses (e.g. indication, length of follow-up) of the subgaleal shunt outside its use for temporary CSF diversion in premature infants with intraventricular hemorrhage and subsequent hydrocephalus. The average length of survival of the primary subgaleal shunt in this population was 32.2 days. We have had good success with subgaleal shunts in children with malignant brain tumors, intraventricular abscesses, chronic truncal wounds, chronic subdural hygromas and meningitis. However, the greatest utility has been in those scenarios in which the peritoneal cavities were not currently, but with time would be, candidates for distal shunt implantation. Examples of these instances are patients with hydrocephalus and necrotizing enterocolitis or hydrocephalus and preoperative abdominal wall pathology such as omphalocele.

Brain Diseases↗
PubMed2003

Parietal foramina are not synonymous with giant parietal foramina.

INTRODUCTION: Enlarged parietal foramina have historically been described as merely the normal parietal foramina (which usually transmit emissary veins connecting the occipital veins to the superior sagittal sinus) in which the diameter exceeds approximately 5.0 mm. METHODS: We have observed well over 500 cadaveric wet and dry specimens for simultaneous bilateral enlarged and normal parietal foramina. RESULTS: We have found two bony adult calvaria, which demonstrate both enlarged parietal 'foramina' and the normally appreciated parietal foramina. CONCLUSIONS: Although a rare occurrence, enlarged parietal foramina occur in conjunction with the normally sized and positioned parietal foramina. This dismisses earlier hypotheses that enlarged parietal foramina are merely parietal foramina that are increased in their diameter.

Adult↗
PubMed2003

Endoscopic third ventriculostomy for hydrocephalus secondary to central nervous system infection or intraventricular hemorrhage in children.

OBJECTIVE: We review our experience of endoscopic third ventriculocisternostomy (ETV) in children with hydrocephalus from central nervous system (CNS) infection or intraventricular hemorrhage to better elucidate success rates and predictors of success in these children. METHODS: We performed a retrospective review of 12 children less than 21 years of age with ETV treated from 1999 to 2002 with a minimum follow-up of 12 months. Children selected for surgery had been diagnosed with hydrocephalus from perinatal germinal matrix hemorrhage or CNS infection and had neuroimaging consistent with obstruction of the aqueduct, fourth ventricular outlets or both at the time of ETV. Charts and imaging studies were reviewed to determine clinical outcomes and predictors of successful ETV. An ETV was deemed successful if the child did not require placement or replacement of a ventriculoperitoneal shunt. RESULTS: Thirteen ETV were performed in 12 patients (7 boys and 5 girls; mean age 9.2 years, range 3.8-21 years), with an overall success rate of 60% for those with CNS infections and 71% for those with perinatal intraventricular hemorrhage at initial presentation. There were no significant complications from the procedure. CONCLUSIONS: ETV is a safe procedure, which in carefully selected children with etiologies of hydrocephalus thought to be 'communicating' in nature carries a satisfyingly high success rate. Further application and study of this modality in larger groups of patients with these causes of hydrocephalus is warranted.

Adolescent↗
PubMed2003

Distances from the atlantal segment of the vertebral artery to the midline in children.

There are scant data in the literature regarding distances from the midline to the suboccipital segment of the vertebral artery, and to our knowledge, none addressing this measurement in the pediatric population. This study seeks to establish age-related distances (Y) from the laterally placed vertebral artery to the midline at the level of the posterior arch of the atlas in children. Measurements from the midline to the most medial portion of the vertebral artery at the level of the posterior arch of the atlas were made in 50 children who underwent CT imaging of the cervical spine. For all left sides, Y = 12-23 mm (mean 17 mm). For all right sides, Y = 10-25 mm (mean 17.5 mm). For girls, Y = 12-16 mm (mean 12.7 mm) for left sides and Y = 12-25 mm (mean 18.5 mm) for right sides. For boys, Y = 12-20 mm (mean 16 mm) for left sides and Y = 10-21 mm (mean 16.7 mm) for right sides. We have found that the most medial portion of the vertebral artery from the midpoint of the posterior arch of the atlas for all ages was approximately 17 and 17.5 mm for left and right sides, respectively. This distance was generally less for left sides, except in the 16-19 years age group. However, as a group, this distance did not vary more than 2.8 mm between left and right sides. These data should assist the neurosurgeon who operates in the suboccipital region in children.

Adolescent↗
PubMed2003

Human horns: a historical review and clinical correlation.

OBJECTIVE: Accounts of bony human horns originating from the cranium are found peppered throughout the early medical literature. This study reviews the extant literature regarding these entities to elucidate their authenticity. METHODS: We reviewed both historical and current literature as well as osteological material from our anatomy laboratories for accounts or observations of bony outgrowths of the calvaria in humans. RESULTS: Human horns seem to be mentioned more frequently in the historical literature and are documented primarily with drawings. Moreover, from early accounts, it is often difficult to distinguish true large bony outgrowths from scalp excrescences. Only two cadaveric specimens from our laboratory were noted to have small anomalous bony protuberances, one on the occiput and one on the frontal bone. CONCLUSION: With the lack of either photographic or extreme dry specimen evidence of such human horns, we would propose that benign calvarial tumors, such as osteomas, may have initiated speculation that such entities, i.e., horns, exist in humans but that scalp lesions, exaggeration, legend, and religious beliefs have historically propagated these entities to a mythical status. In addition, early surgical intervention and changes in nomenclature may have also decreased the frequency of such sightings. Finally, many early descriptions have not been repeated in recent history, even in third-world countries lacking advanced medical care.

Exostoses↗
PubMed2003

Anatomic landmarks for the cervical portion of the thoracic duct.

OBJECTIVE: Avoidance of injury to the thoracic duct during neurosurgical procedures involving the cervical region depends on a working knowledge of its location. This study evaluates superficial anatomic landmarks for the cervical portion of the thoracic duct that may be encountered in neurosurgery of the neck. METHODS: Fifteen dissections of human cadavers were performed to study the relationship between the proximal thoracic duct and superficial landmarks (e.g., the cricoid cartilage and sternal notch of the manubrium). RESULTS: The cervical portion of the thoracic duct was found to be approximated by a roughly 4.4-cm(2) region in the left supraclavicular area beginning approximately 2.0 cm lateral to the midline and 3.5 cm superior to the sternal notch, extending superiorly to a point roughly 3.5 cm from the midline and 2.5 cm inferior to the cricoid cartilage, and terminating within the venous system at a point approximately 4.5 cm lateral to the midline and 3.0 cm superior to the sternal notch. CONCLUSION: Through an increased appreciation for its location, injury to the thoracic duct may be minimized.

Aged↗
PubMed2003

Complications of chronic vagus nerve stimulation for epilepsy in children.

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%).

Adolescent↗
PubMed2003

Atlantoaxial interlaminar distances in cervical flexion in children.

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.

Adolescent↗
PubMed2003

Anomalous traversement of the suprascapular artery through the suprascapular notch: a possible mechanism for undiagnosed shoulder pain?

BACKGROUND: The literature is deficient in studies aimed at quantifying the occurrence of a suprascapular artery traversing the suprascapular notch with the suprascapular nerve. MATERIAL/METHODS: We have performed a cadaveric study using 60 adult specimens (120 sides). Thirty-eight specimens were male and twenty-two were female. RESULTS: Our findings conclude that in this group, the suprascapular artery travels with the suprascapular nerve through the suprascapular notch in 2.5% of specimen sides. Both specimens in whom this occurred were male. CONCLUSIONS: We hypothesize that this anatomic anomaly may also constitute a possible unrecognized mechanism in which shoulder pain is generated. Further studies focused at various races and the presence of this peculiarity are now needed to confirm our findings. In addition, unexplained chronic shoulder pain may be explored with vascular studies aimed at identifying the course of the suprascapular artery.

Adult↗
PubMed2002

Effects of antiepileptic drugs on induced epileptiform activity in a rat model of dysplasia.

Seizure activity associated with cortical dysplasia (CD) is often resistant to standard pharmacologic treatments. Although several animal models exhibit CD, virtually nothing is known about antiepileptic drug (AED) responses in these animals. Here we have used rats exposed to methylazoxymethanol acetate (MAM) in utero, an animal model featuring nodular heterotopia, to investigate the effects of AEDs in the dysplastic brain. 4-aminopyridine (100 microM), a K(+) channel blocker, was used to induce interictal epileptiform bursting in acute hippocampal slices from MAM-exposed and age-matched vehicle-injected control animals. Extracellular field recordings were used to monitor seizure activity in vitro. Five commonly used AEDs were tested: phenobarbital, 25-400 microM; carbamazepine, 25-200 microM; valproate (VPA), 0.19-4 mM; ethosuximide (ESM), 0.5-8 mM; and lamotrigine (LTG), 49-390 microM. 4-AP-induced bursting occurred with shorter latencies in slices from MAM-exposed rats in comparison with slices from controls, confirming the intrinsic hyperexcitability of dysplastic tissue. Each AED tested demonstrated significant burst suppression in control slices, but interictal epileptiform bursting in MAM-exposed slices was resistant to these treatments. Even at the highest concentrations, VPA, ESM and LTG had no effect on burst amplitude in slices from MAM-exposed rats. Pharmaco-resistance was further tested by measuring seizure latencies in awake, freely-moving rats after kainate administration (15 mg/kg, i.p.) with and without pre-treatment with VPA (400 mg/kg i.p.). Pre-treatment with VPA prolonged seizure latency in control rats, but had no effect in MAM-exposed animals. These results suggest MAM-exposed rats exhibit a dramatically reduced sensitivity to commonly prescribed AEDs.

4-Aminopyridine↗
PubMed2002

Focal cooling suppresses spontaneous epileptiform activity without changing the cortical motor threshold.

PURPOSE: Focal cerebral cooling has been shown to reduce epileptiform activity in animals. There are, however, few reports of this phenomenon in humans. METHODS: Electrocorticography was performed before resection of a right frontal tumor in a patient with partial seizures. Cold saline was applied to the interictal spike focus, and its effect on the epileptiform discharges was observed. RESULTS: Application of cold saline to the spike focus resulted in a transient, complete cessation of spiking. This effect was reproduced with a second application of cold saline. The motor threshold for electrical stimulation remained unchanged during the application of saline. CONCLUSIONS: In this patient with tumor-related epilepsy, focal cooling of the cortex reproducibly abolished interictal epileptiform discharges without changing the motor threshold to electrical stimulation.

Adult↗
PubMed2002

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

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 six-fold 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.

Academic Medical Centers↗
PubMedDate not supplied

Exclusive lower extremity mirror movements and diastematomyelia.

Mirror movements usually seen in the Klippel-Feil syndrome are most commonly appreciated in the upper extremities. Lower extremity involvement is seen rarely and when observed, is found in conjunction with upper extremity mirror movements. We report what we believe to be the first case of mirror movements found exclusively in the lower extremities in a female patient presenting with tethered cord syndrome. Our hopes are that this report will help elucidate mechanisms involved with these anomalous movements, as currently there is no commonly accepted etiology.

Adolescent↗