Beyond Dravet and LGS: The Long Tail of Rare Epilepsy

If you read the public materials of most companies working in rare epilepsy, you'll see the same three names again and again: Dravet syndrome, Lennox-Gastaut syndrome (LGS), and developmental and epileptic encephalopathy (DEE) as a broader category.

There are good reasons for that focus. These syndromes are well-defined, have established diagnostic criteria, and represent the most catastrophic and treatment-resistant end of the pediatric epilepsy spectrum. They are also where most of the trial infrastructure already lives.

But rare epilepsy is much wider than three names. The long tail is real, it is severe, and the families inside it tend to feel forgotten by the public discourse.

The shape of the long tail

There are more than 200 identified epileptic syndromes. Many of them are vanishingly rare individually — fewer than 1 in 50,000 live births — but collectively they account for a large fraction of treatment-resistant epilepsy. Below are the syndromes and genetic causes we hear most often from families and researchers, beyond the named three.

CDKL5 deficiency disorder

A genetic disorder caused by mutations in the CDKL5 gene on the X chromosome. Onset is typically in the first three months of life with treatment-resistant seizures, followed by severe developmental delay. Affects approximately 1 in 40,000 to 1 in 60,000 live births, with a strong female predominance. The seizure semiology is variable — infantile spasms, tonic, myoclonic, and complex epileptic spasms all occur in the same patient over time. Nighttime seizures are common and frequently the parents' primary worry.

SCN8A-related epilepsy

A spectrum of disorders caused by mutations in the SCN8A sodium channel gene. Presentation ranges from relatively mild benign familial infantile seizures all the way to severe epileptic encephalopathy with intellectual disability and increased SUDEP risk. SCN8A is notable because it sits in the same gene family as SCN1A (Dravet) — but the treatment paradigm is partially inverted: where Dravet patients are sensitive to sodium-channel blockers, SCN8A patients often benefit from them. Misdiagnosis is a real risk.

Doose syndrome (myoclonic-atonic epilepsy)

Also called Doose syndrome or MAE. Onset usually between 18 months and 5 years, often in previously normally-developing children. The hallmark is myoclonic-atonic seizures — sudden drops — which are alarming to witness and lead to falls and injury. Doose has a more favorable trajectory than Dravet or LGS for many children, with around half achieving meaningful seizure freedom on appropriate therapy. But the drops are unpredictable and the families live with that unpredictability all day, every day.

Rett-epilepsy overlap

Rett syndrome itself is caused by MECP2 mutations and primarily presents as a developmental regression disorder. But somewhere between 60 and 80 percent of Rett patients also develop epilepsy, often beginning in childhood. The seizure types are mixed, and the underlying autonomic instability of Rett means that respiratory and cardiac events overlap with seizure events in ways that are hard to disentangle clinically. Nocturnal monitoring matters more here than in almost any other syndrome described in the literature.

Infantile spasms (West syndrome)

A specific seizure type that defines a critical window in infant brain development. Untreated infantile spasms cause severe developmental regression; early and aggressive treatment with ACTH, vigabatrin, or steroids can change the entire trajectory of a child's life. The clinical urgency around recognizing infantile spasms cannot be overstated. Many of these children later transition into LGS-like phenotypes, but some — especially with genetic causes like TSC, Down syndrome, or CDKL5 — follow distinct paths.

Tuberous sclerosis complex (TSC)

A genetic disorder with tubers in the brain, heart, kidneys, and other organs. Roughly 85 percent of TSC patients develop epilepsy, often beginning as infantile spasms in infancy and evolving into focal epilepsy or LGS-like phenotypes in childhood. TSC is one of the few rare-epilepsy populations with a clearly effective targeted therapy (mTOR inhibitors), which has made it a model for what precision neurology can look like.

Genetic and metabolic causes

Beyond the named syndromes, an increasingly large fraction of rare epilepsy is now attributed to specific gene findings — STXBP1, KCNQ2, GNAO1, PCDH19, GRIN1/2A, SYNGAP1, and dozens of others — many of which were unrecognizable as a category even ten years ago. Whole-exome and whole-genome sequencing has dramatically expanded what families can know about their child's condition, even when no targeted therapy yet exists.

What the long tail shares

These syndromes look very different on paper. They have different ages of onset, different genetics, different prognoses, different first-line treatments. Some have a clear targeted therapy; most do not.

But families in the long tail, in the published literature and advocacy materials, share a striking amount of overlap in their day-to-day experience:

• Unpredictability. Most of these syndromes produce seizures that are poorly anticipated, even by experienced caregivers. The 80 percent no-warning figure cited in general epilepsy estimates appears, anecdotally, to apply even more strongly inside the long tail — this is impression from family and clinician accounts, not a formal long-tail measurement.
• Nocturnal events. Sleep is a common seizure trigger across genetic and structural epilepsies. The clusters that families describe — multiple events on the same night, often during sleep transitions — are nearly universal in the long-tail population.
• Diagnostic delay. The path from first seizure to genetic diagnosis can take years. Families often live with an unspecified epilepsy diagnosis through multiple medication failures before finally getting a name.
• Caregiver vigilance. With no warning and no clear pattern, every parent ends up running their own informal monitoring protocol. We wrote about what that actually looks like — and what it costs.
• Underserved by the literature. The trials, the patient registries, and the public-facing programs are concentrated on the named syndromes. Long-tail families read the same press releases as everyone else and notice their syndrome isn't mentioned.

Why this matters for monitoring

The case for contactless overnight monitoring doesn't depend on which syndrome a child has. It depends on the shape of the problem — unpredictable events, frequent at night, in a child or adult who can't or shouldn't wear a wearable for hours, in a family that can't afford to install a camera or sleep with one eye open every night.

That shape is the same across CDKL5, SCN8A, Doose, Rett-epilepsy overlap, infantile spasms, TSC, and the rest of the long tail. The technology people care about — what's measurable in the bed, what's noisy, what's useful — is the same too.

Where Komori fits

Komori Care is wellness-pathway. We are not a diagnostic. We are not a seizure-detection claim. What we offer is continuous, contactless, multimodal awareness of what is happening overnight in a person's bed — and we are deliberately syndrome-agnostic. The signals matter the same way whether a family is managing CDKL5, Doose, infantile spasms, or unspecified DEE.

We are building toward research partnerships with academic medical centers — including our feasibility amendment in motion with Dr. Mark Quigg at UVA Neurology — and we welcome conversations with foundations, registries, and family communities working anywhere in the long tail.

If your child or your patient is in a syndrome that didn't get its own paragraph above, send us a note. The map is wider than this post can hold.

Sources

• World Health Organization, Epilepsy fact sheet — global prevalence
• ILAE classification of epileptic syndromes (most recent revision)
• Devinsky et al., Lancet Neurology — SUDEP and rare-epilepsy mortality risk
• CDKL5, SCN8A, and STXBP1 family registries for prevalence and natural-history data
• Epilepsy Foundation and the major syndrome-specific foundations (CDKL5 Forum, Dup15q Alliance, STXBP1 Foundation, TSC Alliance, International Foundation for CDKL5 Research) for advocacy and family-experience framing