Table 3.
Clinical Features of Individuals with SLC1A2 Mutations
| Identifier | Age Age, Gender | Epilepsy Syndrome | Development prior to Seizure Onset | Age at Seizure Onset | Seizure Type at Onset | Development after Seizure Onset | Other Seizure Types | Age of Seizure Offset | EEG | Neuroimaging | Other Features | Medicationsa |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Individuals Identified in This Cohort | ||||||||||||
| T23159 | 17 yr, F | EME | never normal | 2 days | myoclonic (virtually continuous multifocal twitching, particularly in sleep) | profound ID | tonic (generalized and focal); myoclonic SE; possible NCSE | ongoing | multifocal; slow background | 3 months— normal; 1 yr—almost complete absence of myelination of cerebrum but normal myelination of cerebellum and brain stem, thin CC, T2 hyperintensity in lentiform nuclei 3 yr— cerebral atrophy, complete absence of myelination of subcortical and periventricular white matter, normal myelination of cerebellum, brain stem, thalami and basal ganglia, thin CC, thinning of cortical gray matter, no cerebellar atrophy; 13 yr—extreme supratentorial atrophy involving cortex, deep gray matter and white matter; sparing of posterior fossa; brainstem and cerebellum are of normal size and signal intensity | Severe asymmetric quadriparesis; gastrostomy; bilateral nephrocalcinosis; amenorrhoea; delayed dentition; frequent bradycardia and hypothermia exacerbated by sleep and anesthesia; progressive microcephaly with bitemporal narrowing; severe growth failure (15 kg at 16 yr); hirsuitism; severe kyphoscoliosis; joint contractures with tapering fingers | CBZ, LTG, LCM, pyridoxine, CZP, AZD, VPA, PB, PHT, prednisolone, VGB, KD, TPM |
| EG1291 | 6 yr, F | EOEE | never normal | 5 days | epileptic spasms | profound ID | myoclonic; myoclonic SE; tonic; tonic-clonic; focal | ongoing | multifocal (no hypsarrhythmia) | 6 months—delayed myelination; 3 yr—progress in myelination, frontal atrophy, thin CC | mild-moderate generalized hypotonia; father had two seizures as an adult, no further seizures while on LTG | LEV, VPA, pyridoxine, VGB, prednisolone, ZNS, KD |
| Individuals Identified in Epi4K Consortium et al., (2013)1 | ||||||||||||
| n | 8 yr, F | IS | unknown | 1 month | focal tonic; myoclonic | some regression; severe ID | unknown | hypsarrhythmia; disorganized background; bifrontal central frequent discharges | normal | blindness; bilateral hamstring contractures; torticollis; extensor plantar response on L and flexor on R; head lag; axial hypotonia; mild appendicular hypertonia | VGB, OCBZ, TPM, PB, LEV | |
Abbreviations are as follows: AZD, acetazolamide; CBZ, carbamazepine; CC, corpus callosum; CLB, clobazam; CLZ, clorazepate; CZP, clonazepam; EE, epileptic encephalopathy; EME, early myoclonic encephalopathy; EOEE, early onset epileptic encephalopathy; F, female; ID, intellectual disability; IS, infantile spasms; KD, ketogenic diet; L, left; LCM, lacosamide; LEV, levetiracetam; LTG, lamotrigine; NCSE, non-convulsive status epilepticus; NG, nasogastric; OCBZ, oxcarbazepine; PB, phenobarbitone; PHT, phenytoin; R, right; SE, status epilepticus; TPM, topiramate; VGB, vigabatrin; VPA, valproate; and ZNS, zonisamide.
a
Medications that were current at the last follow-up are underlined.