Topiramate therapy of epilepsy associated with Angelman's syndrome

Angelman's syndrome, a genetic disorder involving a defect in the DNA coding for subunits of the gamma-aminobutyric acid (GABA) type A receptor, often is associated with intractable epilepsy. Topiramate is a novel anticonvulsant that enhances GABAergic neurotransmission. Five children with Angelman's syndrome and epilepsy were treated with topiramate for clinical indications. The drug was effective and well tolerated, possibly because of its GABAergic properties. Further studies are necessary to confirm and elucidate this observation.

Topiramate

Six studies are cited to demonstrate that topiramate is effective as adjunctive therapy for refractory partial-onset seizures in adults. Subsequent studies indicate that topiramate is also effective as monotherapy in adults and as adjunctive therapy for partial-onset seizures in children, tonic-clonic seizures of nonfocal origin in children and adults, and drop attacks in Lennox-Gastaut syndrome. Adverse effects for adults and children included dizziness, fatigue, ataxia, confusion, somnolence, nephrolithiasis, paresthesia, and weight loss. More adverse effects were observed at higher doses. Topiramate exhibits rapid absorption, long duration of action, and minimal interaction with other antiepileptic drugs.

Efficacy and mortality in treatment of refractory generalized convulsive status epilepticus in children: a meta-analysis

There is no consensus on the choice of drug treatment for refractory generalized convulsive status epilepticus in children. The objective of this meta-analysis of the published literature was to determine the effects of drug treatments on efficacy (seizure cessation) and mortality in children with this condition, controlling for potential confounding factors. One hundred eleven children, treated with diazepam, midazolam, thiopental, pentobarbital, or isoflurane, met strict inclusion criteria. Diazepam was significantly less efficacious than other treatments (P = .006) stratifying for etiology. Overall mortality was 20% in symptomatic cases and 4% in idiopathic cases (P = .038). Mortality was less frequent in midazolam-treated patients (P = .021) stratifying for etiology. Midazolam appears to be a good choice for initial treatment of refractory generalized convulsive status epilepticus in children, but the attribution of differences in efficacy and mortality solely to drug effect is not possible based on the published literature.

Complications and costs of treatment of refractory generalized convulsive status epilepticus in children

Multiple case series in the literature suggest that benzodiazepines and barbiturates are highly efficacious at stopping seizures. Apparent differences in mortality might not be due solely to drug effect. In this systematic review of the medical literature, we assessed the complications and costs of treatment of refractory status epilepticus in 111 children who met strict inclusion criteria, as part of an effort to provide an evidenced-based recommendation for optimal therapy. All children treated with barbiturates required mechanical ventilation, versus 13% of patients treated with benzodiazepines. Benzodiazepine treatment was associated with pressor use in 3.5% of cases, versus 35% with barbiturate treatment. Midazolam treatment was for the shortest duration and allowed the most rapid return to consciousness. Differences in mean 24-hour drug costs were small compared to savings produced by shorter length of treatment and return to consciousness. Benzodiazepines appear to have higher drug costs but lower complications and overall costs than barbiturates.

A double-blind, randomized trial of topiramate in Lennox-Gastaut syndrome. Topiramate YL Study Group

OBJECTIVE

To evaluate the efficacy and safety of topiramate as adjunctive therapy for Lennox-Gastaut syndrome in a multicenter, double-blind, placebo-controlled trial.

BACKGROUND

Conventional antiepileptic drugs are frequently ineffective against multiple-seizure types of Lennox-Gastaut syndrome.

METHODS

Ninety-eight patients >1 year to <30 years of age, with slow spike-and-wave patterns on EEG, seizure types including drop attacks, and either a history of or active atypical absence seizures, were assigned to an 11-week, double-blind treatment phase with either topiramate or placebo. Topiramate was titrated to target doses of approximately 6 mg/kg/d.

RESULTS

For drop attacks, the most severe seizures associated with this syndrome, the median percentage reduction from baseline in average monthly seizure rate was 14.8% for the topiramate group and -5.1% (an increase) for the placebo group (p = 0.041). Topiramate-treated patients demonstrated greater improvement in seizure severity than did placebo-treated patients based on parental global evaluations (p = 0.037). The percentage of patients with a > or = 50% reduction from baseline in major seizures (drop attacks and tonic-clonic seizures) was greater in the topiramate group (15/46 or 33%) than in the control group (4/50 or 8%; p = 0.002). The most common adverse events in both groups were CNS related; there were no discontinuations from topiramate therapy due to adverse events.

CONCLUSIONS

Topiramate adjunctive therapy was effective in reducing the number of drop attacks and major motor seizures and in improving seizure severity as determined by parental global evaluation.

Racial differences in free radical scavenging enzyme activity in children

Oxygen-derived free radicals play an important role in multiple pediatric neurologic diseases. Five intracellular free radical scavenging enzymes and three trace elements provide a significant portion of the body's defenses against free radical-mediated injury. Although the effects of age, sex, and ethnicity on the body's antioxidant defenses have been described, no study has examined whether racial differences exist. This pilot study sought to determine the effect of racial differences on the activity of five free radical scavenging enzymes and the concentrations of three associated trace elements in normal, healthy American children. The erythrocyte and plasma activities of five major free radical scavenging enzymes (glutathione peroxidase, glutathione reductase, glutathione-S-transferase, catalase, and superoxide dismutase) and plasma concentrations of three associated trace elements (selenium, copper, and zinc) were determined for 83 healthy American children, aged 1 to 18 years. One- and two-way interactions of race, age, and sex with each dependent variable were analyzed. African-Americans had higher erythrocyte glutathione peroxidase activity, erythrocyte superoxide dismutase activity, and selenium and copper concentrations than Caucasians. Racial inequalities do exist in free radical scavenging enzyme activity and trace element concentration in healthy children. African-American children had higher activity in the two most important free radical scavenging enzymes used by the brain compared to age- and sex-matched Caucasian children. Future clinical research in free radical-mediated pediatric neurologic diseases needs to consider race along with age and sex in both study design and data analysis.

Topiramate pharmacokinetics in infants

PURPOSE

This study's goal was to provide preliminary data on the pharmacokinetics of topiramate (TPM) in a cohort of infants (younger than 4 years) participating in an open-label trial of TPM in refractory infantile spasms.

METHODS

The pharmacokinetics of TPM were assessed in infants receiving a stable TPM dose for >7 days during the extension phase of this trial. Blood samples were drawn just before and 0.5. 1, 1.5, 2, 4, 6, 8, and 12 h after the morning TPM dose. TPM plasma concentrations were determined by fluorescence polarization immunoassay. The noncompartmental analysis module of WinNonlin was used to calculate individual patient pharmacokinetics profiles.

RESULTS

Five infants (ages, 23.5-29.5 months) formed the study cohort. These infants had been given TPM for a median of 9 months (range, 6-11 months) and were currently receiving between 11 and 38.5 mg/kg/day TPM. One was receiving TPM monotherapy, whereas four were taking concomitant antiepileptic medications (AEDs; n = 2, enzyme-inducing agents; n = 2, non-enzyme-inducing drugs). TPM pharmacokinetics in infants appears to be linear. In this cohort, mean TPM plasma clearance (CL/F, 66.6+/-27.4 ml/h/kg) was slightly higher than that reported for children and adolescents and therefore substantially higher than that reported for adults. TPM CL/F was higher and the calculated half-life shorter in the infants receiving concomitant enzyme-inducing AEDs.

CONCLUSIONS

Based on this small cohort of patients, it appears that infants may require significantly larger TPM doses, based on weight, than children, adolescents, or adults. Titration to effect and not absolute TPM dose should guide therapy in this age group.

Automated microanalysis of gabapentin in human serum by high-performance liquid chromatography with fluorometric detection

An automated high-performance liquid chromatographic method for the determination of gabapentin, 1-(amino-methyl)cyclohexaneacetic acid, in serum is described. The procedure involves protein precipitation with methanol followed by using a robotized derivatization with o-phthaldialdehyde reagent and automated high-performance liquid chromatography. The analog of gabapentin, 1-(aminomethyl)cycloheptaneacetic acid, was used as the internal standard. Blank serum was fortified with gabapentin (0.1-10.0 microg/ml) and internal standard. Separation was achieved on a Waters 5-microm reversed-phase column (10 cmx4.6 mm) with mobile phase consisting of 0.02 M phosphate buffer (pH 4.5)-acetonitrile (50:50, v/v). Eluents were monitored by fluorescence spectroscopy with excitation and emission wavelengths of 230 and 420 nm, respectively. The calibration curve for gabapentin in serum was linear (r=0.999) over the concentration range 0.1-10.0 microg/ml. The inter- and intraassay variations for three different gabapentin concentrations were < or =10% throughout. The lower limit of quantitation was found to be 0.1 microg/ml. Chromatography was unaffected by a range of commonly employed antiepileptic drugs or selected amino acids.

A double-blind, randomized trial of topiramate as adjunctive therapy for partial-onset seizures in children. Topiramate YP Study Group

OBJECTIVE

To evaluate the efficacy and safety of topiramate 6 mg/kg/day in children (age 2 to 16 years) as adjunctive therapy for uncontrolled partial-onset seizures with or without secondarily generalized seizures in a multicenter, randomized, double-blind, placebo-controlled trial.

METHODS

Patients with at least six partial-onset seizures during the 8-week baseline phase were treated with either topiramate (n = 41) or placebo (n = 45) for 16 weeks.

RESULTS

Topiramate-treated patients had a greater median percent reduction from baseline in average monthly partial-onset seizure rate than placebo-treated patients (33.1% versus 10.5%, p = 0.034), a greater proportion of treatment responders (i.e., patients with a > or = 50% seizure rate reduction; 16 of 41 [39%] versus 9 of 45 [20%], p = 0.080), and patients with a > or = 75% seizure rate reduction (7 of 41 [17%] versus 1 of 45 [2%], p = 0.019), and better parental global evaluations of improvement in seizure severity (p = 0.019). Emotional lability (12% versus 4%), fatigue (15% versus 7%), difficulty with concentration or attention (12% versus 2%), and forgetfulness/impaired memory (7% versus 0%) were more frequent among topiramate-treated than placebo-treated patients. Most treatment-emergent adverse events were mild or moderate in severity. No topiramate-treated patients discontinued the study due to adverse events.

CONCLUSIONS

Topiramate was safe and effective in the treatment of partial-onset seizures in children.

A pilot study of topiramate in the treatment of infantile spasms

PURPOSE

West syndrome is a rare epileptic syndrome associated with infantile spasms, a specific abnormal electroencephalographic pattern (termed hypsarrhythmia), and mental retardation. Management of this disorder is difficult because current treatment regimens, including many anticonvulsants and hormones, are often ineffective. Topiramate (TPM) is a new antiepileptic drug that may be effective in pediatric epilepsies. We conducted a pilot study to test the effects of rapid TPM dosing in patients with refractory infantile spasms.

METHODS

Eleven children with refractory infantile spasms were given an initial dose of 25 mg TPM per day in addition to their current therapy. Dosage was increased by 25 mg every 2-3 days until spasms were controlled, the maximal tolerated dose was reached, or the maximal dose of 24 mg/kg/day was achieved. Efficacy was primarily assessed by video EEG and secondarily by parental count of spasm frequency.

RESULTS

Five (45%) subjects became spasm free during the study, with absence of infantile spasms and hypsarrhythmia (either classic or modified) proven by video EEG. Nine subjects, including the five spasm free, achieved a spasm reduction of > or =50%. Spasm frequency decreased from 25.6+/-19.3 to 6.9+/-5.9 spasms/day. Sixty-four percent of the subjects were able to achieve TPM monotherapy.

CONCLUSIONS

Results in this cohort of 11 patients with refractory disease show TPM to be a promising new agent for the treatment of infantile spasms.

Need for electroencephalogram video confirmation of atypical absence seizures in children with Lennox-Gastaut syndrome

Children with childhood epileptic encephalopathy (Lennox-Gastaut syndrome) frequently have both multiple seizure types and nonepileptic stereotyped events that are difficult to differentiate. We hypothesize that electroencephalogram (EEG) video monitoring is essential for correct identification of atypical absence seizures in this population. All video/EEG monitoring records on patients with confirmed Lennox-Gastaut syndrome between September 1992 and December 1996 were reviewed for clinical events and EEG changes. A subset of patients with suspected atypical absence seizures during the video/EEG formed the cohort for analysis. Thirty-eight patients had 48 monitoring periods ranging from 1 to 4 days (mean, 2.2 days). Twenty-six monitoring periods captured suspected atypical absence seizures and formed the study cohort. Suspected atypical absence seizures were epileptic seizures in only 27% (7 of 26) of the study cohort. By contrast, parents reliably and correctly identified tonic, atonic, and tonic-clonic seizures in the study cohort. Reliable diagnosis and subsequent counting of atypical absence seizures in patients with Lennox-Gastaut syndrome cannot be made on the basis of observation and/or history alone. Future outpatient studies of investigational anticonvulsant medications for patients with Lennox-Gastaut syndrome should consider parental counts of atypical absence seizures unreliable. We recommend that video/EEG monitoring be done on all Lennox-Gastaut syndrome patients with suspected atypical absence seizures not controlled by medication.

Altered antioxidant enzyme activities in children with a serious adverse experience related to valproic acid therapy

Specific oxidative metabolites of valproic acid (VPA) have been associated with the clinically defined toxicity of the drug. To investigate the role of enzymatic detoxification in clinical toxicity, we compared activities of five antioxidant enzymes in 15 patients with a serious adverse experience (SAE) related to VPA therapy, to enzyme activities measured in 35 patients with good clinical tolerance of VPA, and 50 healthy, age-matched subjects. These enzymes included glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione transferase, superoxide dismutase, and catalase in erythrocytes; and GSH-Px in plasma. We also determined levels of Se, Cu, and Zn, trace elemental cofactors for these enzymes, in plasma from each individual. In patients with a VPA-associated SAE, GSH-Px was significantly depressed and GSSG-R was significantly elevated relative to values for the other groups. Selenium and zinc concentrations were lower in SAE patients than in controls. These findings may indicate a role for selenium dependent antioxidant activity in individual susceptibility to an SAE related to VPA therapy.

Topiramate use in pediatric patients

Topiramate (TPM), a new antiepileptic medication, is efficacious as adjunctive therapy in adults with partial onset seizures. Its efficacy as adjunctive therapy in children was evaluated in two randomized double-blind placebo-controlled trials involving childhood epileptic encephalopathy (the Lennox-Gastaut syndrome) and partial onset seizures. In these studies, topiramate adjunctive therapy resulted in a significant reduction in drop attacks (tonic or atonic seizures) in patients with the Lennox Gastaut syndrome and a significant reduction in partial onset seizures in children with refractory partial epilepsy. In both trials, TPM's efficacy improved as the dose escalated from the double-blind phase to the open-label portion. The minimally effective topiramate dose for adjunctive therapy in children with refractory epilepsy appears to be 6 mg/kg/day. Topiramate was well tolerated with mild or moderate side effects, predominantly related to the central nervous system. Practical tips are provided that may increase the chance that topiramate will be effective and well tolerated. The most important advice is a "start low, go slow" approach. An initial TPM dose of 0.5-1 mg/kg/day followed by weekly increments of 0.5-1 mg/kg is usually well tolerated. Based on these studies, topiramate appears to be an important addition to our pediatric AED armamentarium.

Short-term and long-term memory in early temporal lobe dysfunction

Following medial temporal damage, mature humans are impaired in retaining new information over long delays but not short delays. The question of whether a similar dissociation occurs in children was addressed by testing children (ages 7-16) with unilateral temporal lobe epilepsy (TLE) and controls on short- and long-term memory tasks, including a spatial delayed response task (SDR). Early-onset TLE did not affect performance on short delays on SDR, but it did impair performance at the longest delay (60 s), similar to adults with unilateral medial temporal damage. In addition, early-onset TLE affected performance on pattern recall, spatial span, and verbal span with rehearsal interference. No differences were found on story recall or on a response inhibition task.

Topiramate

Clinical evidence is emerging that topiramate (TPM) may be effective in pediatric epilepsies. Topiramate pharmacokinetics appear to be linear in children when administered in dosages up to 9 mg/kg/d. Mean oral clearance is 44% to 54% higher in children when compared with historical data from adults; steady-state plasma TPM concentrations for the same mg/kg dose are expected to be 33% lower in children. While double-blind, placebo-controlled trials of adjunctive TPM therapy in Lennox-Gastaut syndrome, primary generalized tonic-clonic seizures, and refractory partial-onset seizures in children are ongoing, preliminary results of pilot studies and the open-label extension phases of these double-blind studies suggest TPM may be effective as adjunctive therapy in a broad range of seizure disorders. In the open-label extension phase of a double-blind trial, the proportion of patients with Lennox-Gastaut syndrome experiencing 50% or greater reduction in seizures was 47%. Likewise, seizures were reduced 50% or more with TPM adjunctive therapy in 64% of children with partial-onset seizures and in 67% of patients with primary generalized tonic-clonic seizures treated with open-label during the extension phase of two separate double-blind studies. Preliminary experience suggests that TPM monotherapy can be successfully substituted for another antiepileptic drug in some children. The results of the well-controlled trials are needed to confirm these preliminary observations of TPM effectiveness in pediatric epilepsies.

Preliminary observations on topiramate in pediatric epilepsies

Preliminary results of studies of topiramate (TPM) in children are now available. In a pharmacokinetic study among 18 male and female children, target daily dosages of up to 9 mg/kg/day were evaluated. TPM pharmacokinetics in children were linear. Mean TPM oral clearance (CL/F) was 44-54% higher in children [depending on concomitant antiepileptic drugs (AEDs)] compared with historical data from adults, and steady-state plasma TPM concentrations for the same mg/kg dose were 33% lower in children compared with historical adult data. In a long-term, open-label pilot study of adjunctive TPM therapy in 18 patients with Lennox-Gastaut syndrome, six of the eight patients (75%) still receiving TPM report a greater than 50% reduction in total seizures, with the best results observed in tonic-atonic, atypical absence, and generalized tonic-clonic seizures. Subsequent large double-blind, placebo-controlled trials of adjunctive TPM therapy in Lennox-Gastaut syndrome and refractory partial-onset pediatric epilepsy are ongoing, with high percentages of enrolled patients in both studies completing double-blind treatment and entering long-term TPM open extension trials. A small TPM monotherapy substitution trial in children with well controlled partial onset seizures showed that TPM monotherapeutic substitution can be achieved successfully with an acceptable amount of adverse experiences with a weekly increase of 1 mg/kg/day to a maximal dose of 3 mg/kg/day. These preliminary results suggest that TPM may be a useful new AED in pediatric patients with a variety of seizure disorders.

Lamotrigine adjunctive therapy in childhood epileptic encephalopathy (the Lennox Gastaut syndrome)

PURPOSE

We assessed efficacy and safety of adjunctive lamotrigine (LTG) therapy in patients with the Lennox-Gastaut syndrome (LGS).

METHODS

The study was a single-center, retrospective chart review of open-label adjunctive LTG therapy in patients with LGS. Initial LTG dose and titration was dependent on concomitant antiepileptic drugs (AEDs). Efficacy was based on the change in seizure frequency between the initiation of LTG therapy and December 1, 1995 (or LTG discontinuation). Seizure diaries were used to count patient seizures. A secondary evaluation of efficacy was a parental or guardian assessment of the patient's global status. The evaluation of safety involved chart review for treatment-emergent adverse events (AE).

RESULTS

Data from 16 LGS patients were analyzed. Fifty-three percent (8 of 15) had a > 50% reduction in seizure frequency with LTG adjunctive therapy. Tonic, atonic, generalized tonic-clonic (GTCS), and atypical absence seizure frequency but not myoclonic seizure frequency decreased significantly during LTG therapy. Fifty-three percent of the patient's parents (8 of 15) reported that their child's quality of life (QOL) was much or very much improved during the study. The major treatment-emergent AE were infection (50%, 8 of 16) and sleep disturbance (19%, 3 of 16). A rash was noted in 13% (2 of 16) of the patients and resulted in LTG discontinuation in 1. No clinically significant changes were noted in neurologic examination or laboratory tests during the study.

CONCLUSIONS

Our results indicate that LTG adjunctive therapy is effective and well tolerated in patients with LGS.

Pediatric epilepsy syndromes

The development of an international classification for epilepsies and epileptic syndromes has led to substantial progress in the understanding and treatment of patients with epilepsy. Epilepsies and epileptic syndromes are partitioned first by seizure type and then by etiology. This manuscript describes recent advances in six major pediatric epilepsy syndromes. The first three discussed (benign childhood epilepsy with centrotemporal spikes, juvenile myoclonic epilepsy, and childhood absence epilepsy) are the three most common epilepsy syndromes, and each has been the focus of significant research. Patients with benign childhood epilepsy with centrotemporal spikes (benign rolandic epilepsy) may not require anticonvulsant therapy, and their seizures always remit by midadolescence. Juvenile myoclonic epilepsy was the first major epilepsy syndrome for which a gene locus was found. The underlying neuronal pathways and cellular mechanisms of the generalized absence seizures of childhood absence epilepsy are well delineated. The last three syndromes discussed (West syndrome, Lennox-Gastaut syndrome, and acquired epileptic aphasia) are devastating catastrophic epileptic syndromes. The focus of research in West syndrome (infantile spasms) has been to develop better therapeutic interventions (both medical and surgical) and an improved understanding of its pathogenesis. New effective medications are available for patients with Lennox-Gastaut syndrome (childhood epileptic encephalopathy), but one of them (felbamate) has been associated with previously unrecognized serious side effects. Lastly, acquired epileptic aphasia is an example of a poorly understood epilepsy syndrome. A multicenter group has been organized to reexamine this syndrome and produce a better understanding of its pathogenesis and treatment.

Comparison of erythrocyte antioxidant enzyme activities and embryologic level of neural tube defects

Increased exposure to oxidant-derived free radicals or inadequate systems for antioxidant defense could alter cellular response at critical points in development. We measured 5 antioxidant enzymes, glutathione peroxidase (GSH-Px), glutathione reductase, glutathione-S-transferase, catalase and superoxide dismutase in erythrocytes and their plasma cofactor trace elements (Se, Zn, Cu) in 37 children with myelomeningocele and in 37 age-matched controls. We placed the patients into 3 groups according to motor level of the lesion at birth. We found significantly lower GSH-Px activities (p = 0.007) in children with myelomeningocele. For paired comparisons among the 3 patient groups and controls, there were significant differences (p < 0.05) between controls and both high (thoracic) and raid (lumbar) level embryologic lesions. The finding of antioxidant enzyme variations in our patients with myelomeningocele may indicate a role for abnormal oxidative metabolism in the development of this defect. The contribution of oxidative stress to human birth defects warrants investigation. We discuss potential relationships between oxidative stress and energy metabolism during primary neurulation.

Cerebral infarction in sickle cell disease: transcranial Doppler US versus neurologic examination

PURPOSE

To evaluate flow velocity measurements in the middle cerebral artery (MCA) and/or neurologic examination for detection of cerebral infarction in sickle cell disease (SCD).

MATERIALS AND METHODS

Twenty-four pediatric patients aged 6 1/2-17 years with SCD underwent magnetic resonance (MR) imaging, MR angiography, neurologic examination, and transcranial Doppler ultrasonography (US). Transcranial Doppler studies were evaluated for maximum flow velocity in the right and left MCAs. Combinations of cut-off values were used to determine the sensitivity and specificity of transcranial Doppler US for detection of infarction.

RESULTS

Neurologic examination had 58% sensitivity and 92% specificity for cerebral infarction. Maximal flow velocity > 200 cm/sec or < 100 cm/sec (including no flow) helped identify nine of 12 patients with infarcts proved at MR imaging, with only one false-positive result (sensitivity, 75%; specificity 92%). The combination of neurologic examination and transcranial Doppler US produced 92% sensitivity and 83% specificity for cerebral infarction.

CONCLUSION

The combination of transcranial Doppler US and neurologic examination has potential as a screening technique for infarction in SCD.

Accuracy of neurologic examination and history in detecting evidence of MRI-diagnosed cerebral infarctions in children with sickle cell hemoglobinopathy

We determined the accuracy of neurologic examination and the history of a previous neurologic event in detecting clinical evidence of a magnetic resonance imaging (MRI)-diagnosed cerebral infarction in 30 children with sickle cell hemoglobinopathy. Each patient had an MRI of the brain, neurologic examination, chart review, and psychometric evaluation. Seventeen children (57%) had MRI evidence of cerebral infarction based on demonstration of parenchymal abnormalities in a vascular distribution. Among the 17 children with MRI evidence of cerebral infarction, only 12 (71%) had an abnormal neurologic examination, and 11 (65%) had a history of a prior neurologic event. In contrast, among the 13 children with normal MRIs, 12 (92%) had normal neurologic examinations, and no child had a previous history of a neurologic event. Multiple, bilateral, heterogeneous cerebral infarctions frequently occur without overt neurologic signs or symptoms in children with sickle cell hemoglobinopathy. Previous studies that relied on a focal neurologic examination or a history of a neurologic event to identify cerebral infarctions in patients with sickle cell hemoglobinopathy most likely underrepresented the true frequency of cerebral infarctions in this population. Future prospective studies of cerebral infarctions in children with sickle cell hemoglobinopathy should include MRIs for identification and classification, rather than neurologic examination or clinical history alone.

Noninvasive central nervous system imaging in sickle cell anemia. A preliminary study comparing transcranial Doppler with magnetic resonance angiography

PURPOSE

We evaluated the accuracy of transcranial Doppler (TCD) and magnetic resonance angiography (MRA) as a screening modality for cerebral infarct in patients with sickle cell disease.

PATIENTS AND METHODS

Twenty-four patients with sickle cell disease were assessed for a cerebral infarct. Each patient underwent neurologic examination, psychometric evaluation, magnetic resonance imaging (MRI), MRA, and TCD. Presence of a cerebral infarct was determined by an MRI and supported by neurologic and neuropsychometric evaluation. All investigators were unaware of the patient's status. Cerebral vasculature by MRA was categorized as being occluded, stenotic, or normal. The maximum TCD velocity of the right and left middle cerebral artery were assessed. Various cutoffs were used to determine the sensitivity and specificity of TCD.

RESULTS

MRA had a sensitivity and specificity of 100% and 92%, respectively. At a maximum velocity cutoff of 180 cm/s, the sensitivity and specificity of TCD were 20% and 67%, respectively. No maximum velocity on TCD produced both sensitivity and specificity > 50%.

CONCLUSION

MRA is more sensitive than TCD when the middle cerebral artery for maximum velocity is compared. Prospective evaluation is warranted to determine if TCD is useful as a screening technique for cerebral infarction in children with SCD.

Reversible metabolic myopathy in biotinidase deficiency: its possible role in causing hypotonia

A 5-year-old girl diagnosed with biotinidase deficiency at 9 months of age demonstrated limb and axial hypotonia which improved on biotin therapy. In this patient, electromyographic (EMG) studies prior to treatment were compatible with a mild myopathic process. Serial EMGs performed on biotin therapy demonstrated a gradual resolution of the myopathy. This is the first documented case of a reversible myopathy in a patient with biotinidase deficiency, which may contribute to the clinical findings of hypotonia.