The gain of function SCN1A disorder spectrum: novel epilepsy phenotypes and therapeutic implications.

Brain voltage-gated sodium channel NaV1.1 (SCN1A) loss-of-function variants cause the severe epilepsy Dravet syndrome, as well as milder phenotypes associated with genetic epilepsy with febrile seizures plus. Gain of function SCN1A variants are associated with familial hemiplegic migraine type 3. Novel SCN1A-related phenotypes have been described including early infantile developmental and epileptic encephalopathy with movement disorder, and more recently neonatal presentations with arthrogryposis. Here we describe the clinical, genetic and functional evaluation of affected individuals. Thirty-five patients were ascertained via an international collaborative network using a structured clinical questionnaire and from the literature. We performed whole-cell voltage-clamp electrophysiological recordings comparing sodium channels containing wild-type versus variant NaV1.1 subunits. Findings were related to Dravet syndrome and familial hemiplegic migraine type 3 variants. We identified three distinct clinical presentations differing by age at onset and presence of arthrogryposis and/or movement disorder. The most severely affected infants (n = 13) presented with congenital arthrogryposis, neonatal onset epilepsy in the first 3 days of life, tonic seizures and apnoeas, accompanied by a significant movement disorder and profound intellectual disability. Twenty-one patients presented later, between 2 weeks and 3 months of age, with a severe early infantile developmental and epileptic encephalopathy and a movement disorder. One patient presented after 3 months with developmental and epileptic encephalopathy only. Associated SCN1A variants cluster in regions of channel inactivation associated with gain of function, different to Dravet syndrome variants (odds ratio = 17.8; confidence interval = 5.4-69.3; P = 1.3 × 10-7). Functional studies of both epilepsy and familial hemiplegic migraine type 3 variants reveal alterations of gating properties in keeping with neuronal hyperexcitability. While epilepsy variants result in a moderate increase in action current amplitude consistent with mild gain of function, familial hemiplegic migraine type 3 variants induce a larger effect on gating properties, in particular the increase of persistent current, resulting in a large increase of action current amplitude, consistent with stronger gain of function. Clinically, 13 out of 16 (81%) gain of function variants were associated with a reduction in seizures in response to sodium channel blocker treatment (carbamazepine, oxcarbazepine, phenytoin, lamotrigine or lacosamide) without evidence of symptom exacerbation. Our study expands the spectrum of gain of function SCN1A-related epilepsy phenotypes, defines key clinical features, provides novel insights into the underlying disease mechanisms between SCN1A-related epilepsy and familial hemiplegic migraine type 3, and identifies sodium channel blockers as potentially efficacious therapies. Gain of function disease should be considered in early onset epilepsies with a pathogenic SCN1A variant and non-Dravet syndrome phenotype.

Characterization of standard work tools for intrathecal baclofen therapy.

PURPOSE: Intrathecal baclofen (ITB) has been an effective therapy since the 1980s, with widely reported revision, infection, and complication rates. Publications targeting surgical workflow have resulted in decreased infection and revision rates, but a standard workflow for the entire pathway has not been described. To present, define, and test standard work tools for patients receiving ITB to promote uniformity and standard of care in the field. METHODS: A multidisciplinary approach from the movement disorder program of a tertiary care center defined all steps comprising the ITB pathway, and then developed standard work tools to decrease variability with respect to preoperative workup, day of surgery protocol, post-operative care, and also evaluation and treatment with respect to pump infection or malfunction. RESULTS: Defined steps used at specific points of ITB pathway are presented with a single institution's outcome using the protocol from July 2017 to November 2020. A total of 60 procedures were performed. The overall complication rate was 14.5% at 6 months. Complications included an infection rate of 3.6% at 6 months, wound revision rate of 1.8% at 6 months, CSF leak rate of 1.7% at 6 months, and a 30-day readmission rate related to initial surgery of 6.7%. CONCLUSIONS: Workflow efficiency and optimization for ITB patients can be used to obtain lower complication rates compared to historical cohorts in literature. A single-center, retrospective review highlights this.

Pre- and Postoperative Gait Analysis and Video for Selective Dorsal Rhizotomy in Spastic Diplegia: 2-Dimensional Operative Video.

Severe lower limb spasticity can hinder motor tasks and negatively impacts the quality of life in patients with cerebral palsy. Selective dorsal rhizotomy is a well-established neurosurgical intervention aimed at reducing muscle spasticity in patients with such neuromuscular conditions. Long-term outcomes of selective dorsal rhizotomy have been promising among the authors' institutional series of patients. In this case, we demonstrate the use of L1-S1 osteoplastic laminoplasty and L1-S1 selective dorsal rhizotomy in a 5-year-old male patient with cerebral palsy and spastic lower extremity diplegia. Favorable selection criteria for this case included disabling lower extremity diplegia, young age, good core strength, no cognitive delay, and strong rehabilitation potential. The patient's preoperative functional status was noncommunity ambulator (Gross Motor Function Classification System Level III) with walker use and good dynamic balance. Prior to the procedure, he demonstrated an overall decreased muscle strength in bilateral lower extremities with bilateral hamstring spasticity (Ashworth 3) and bilateral heel cord spasticity (Ashworth 4). Rhizotomy was performed with identification and selective sectioning of dorsal nerve roots with abnormal stimulation patterns. Fibers with unsustained discharge of appropriate muscles were identified and spared. No intraoperative or postoperative complications were encountered. The patient had minimal back pain and surgical morbidity postoperatively. Following the procedure and highly structured inpatient and outpatient rehabilitation therapies, the patient exhibited significant improvement in gait velocity (84%) and gait cadence (66%) at 5 months. Additionally, the patient demonstrated greater independence of activities of daily living and improvements in mobility by Pediatric Evaluation Disability Index. Patient consent was obtained from the parent.

Simultaneous toxicities in a child on multiple anticonvulsants.

It is rare to develop simultaneous toxicities while on anticonvulsants. This article presents a 3(1/2)-year-old child on valproic acid, lamotrigine, and phenytoin who developed simultaneous hepatotoxicity and bone marrow toxicity during a parainfluenza virus type 3 infection. These toxicities resolved after the cessation of anticonvulsants, and her seizures were managed acutely with scheduled lorazepam. This article discusses the possibility that simultaneous use of valproic acid, lamotrigine, and phenytoin could give this combination of toxicities and that concurrent viral infection may increase this risk.