Myo-Inositol Supplementation Reduces Seizures in Rare Childhood Epileptic Encephalopathy

Developmental and Epileptic Encephalopathies (DEEs) are among the most severe and treatment-resistant neurological conditions in childhood, associated with lifelong disability and early mortality. PLCB1 encodes phospholipase C beta-1, an enzyme central to phosphoinositide signaling. Loss-of-function variants or deletions in PLCB1 impair the downstream inositol phosphate cascade, depleting intracellular and extracellular myo-inositol at synapses. The rationale for supplementation rests on the idea that restoring synaptic myo-inositol might re-establish normal membrane dynamics and reduce the pathological neuronal hyperexcitability characteristic of DEE.

The clinical case centers on a boy diagnosed with PLCB1-related DEE who had failed multiple standard antiseizure medications. The research team at Boston Children's Hospital initiated chronic enteral myo-inositol supplementation as an add-on therapy. Myo-inositol levels were serially monitored across three compartments — plasma, urine, and CSF — using stable isotope dilution with selected ion monitoring gas chromatography/mass spectrometry (GC/MS), a highly sensitive and quantitative analytical method. Brain structure and function were tracked longitudinally through magnetic resonance spectroscopy (MRS), structural MRI, and EEG recordings, providing a multimodal picture of treatment response.

The treatment was well tolerated with no reported adverse events throughout the monitoring period, satisfying FDA-aligned safety requirements. Clinically, the patient demonstrated a meaningful reduction in seizure burden alongside radiographic stabilization of brain atrophy — an outcome that was most pronounced during the first and second years of life when the brain is at its most plastic and vulnerable. CSF myo-inositol levels rose with supplementation, indicating that enteral dosing can successfully penetrate the blood-brain barrier or the choroid plexus pathway to elevate CNS concentrations, a non-trivial pharmacokinetic finding for this hydrophilic molecule.

To mechanistically substantiate the treatment rationale, the team employed a Slc5a3 knockout mouse model — mice lacking the sodium/myo-inositol cotransporter 2 gene, which is critical for CNS inositol transport. Knockout pups born to untreated carrier mothers die perinatally. When pregnant Slc5a3 carrier mice were administered myo-inositol supplementation, CSF myo-inositol content in the knockout pups was measurably increased, and crucially, this intervention prevented their death. This preclinical finding provides strong mechanistic support for the hypothesis that extracellular synaptic myo-inositol plays an essential and previously underappreciated role in prenatal and early postnatal brain development and survival.

The proposed mechanism links myo-inositol to membrane potential regulation: the molecule may help maintain a fetal-like hyperpolarized state in developing neurons, thereby raising the threshold for pathological firing. This is conceptually distinct from conventional antiseizure drug mechanisms (sodium channel blockade, GABAergic enhancement, etc.) and represents a potentially orthogonal treatment strategy. The authors argue this is particularly relevant in early infancy when neuronal excitability is intrinsically high and when DEE seizures are most devastating and refractory. Given the favorable tolerability, accessible formulation, and supportive preclinical data, the authors call for prospective clinical trials of high-dose myo-inositol in infants with severe epileptic encephalopathy, particularly those with disrupted phosphoinositide signaling pathways.