Epilepsy A-Z: Common and Rare Types of Epilepsy (Part 3)

Lafora Disease

Lafora progressive myoclonic epilepsy, MELF, Lafora body disease, myoclonic epilepsy of Lafora and progressive myoclonic epilepsy type 2.

Occipital and/or myoclonic seizures that start in late childhood or early adolescence and worsen over time. Seizures are accompanied by changes in behavior, depression, confusion, problems with speech (dysarthria) which progress into dementia, spasticity and sometimes status epilepticus (prolonged seizure activity). This form of epilepsy is fatal. It presents in childhood or adolescence.

Motion, excitement, and flashing lights

Unknown but MELF is more common in certain areas of the world.

Caused by mutations in the EPM2A gene or the NHLRC1 gene. It is an autosomal recessive disorder (see below).

Generalized to more than one part of the brain.

The life expectancy after the first symptoms appear is up to 10 years.

Jargon Alert!

Autosomal recessive disorder = both copies of a defective gene are required for the person to have the disease, disorder or trait.

Myoclonic Epilepsy with Ragged Red Fibers (MERFF)

Merrf syndrome.

Myoclonus (twitching muscle spasms), ataxia (limited coordination), peripheral neuropathy, generalized epileptic seizures and mitochondrial dysfunction seen as ragged-red fibers in muscle biopsies. Other MERFF symptoms can include hearing and sight loss, limited stature and heart problems.

None specific to MERFF.

Rare. Exact prevalence is unknown.

Caused by mutations in the MT-TK gene in 80% of cases. Other genes have been reported but they are commonly cited in other mitochondrial disorders (see below) as well.

Generalized to more than one part of the brain.

Varies but often poor with limited life expectancy.

Jargon Alert!

Mitochondrial disorders = mitochondria  are the power generators of the cell. These organelles make over 90% of the body’s energy supply. If they are functioning suboptimally, the cell has less energy available to it and may die. If this occurs systemically, the body will experience organ failure. Mitochondrial disorders is the name given to an extensive group of heterogeneous diseases, including MERFF.

Neuronal Ceroid Lipofuscinoses (NCLs)

Batten disease.

Progressive intellectual and motor deterioration, seizures, and early death. Vision problems are common. NCLs are a group of inherited, neurodegenerative, lysosomal storage disorders. The clinical phenotype of NCLs are classified into four main types according to age of onset and and subgroups by the gene responsible.

None specific to NCLs.

Up to 1 in 12,500 people in some populations but 2 to 4 of every 100,000 in the US.

Autosomal recessive or dominant inheritance depending on the type. There are many genes involved depending on the subtype of the disorder.

Generalized to more than one part of the brain.

Life expectancy varies with the type of the disorder but it is fatal but no cure found thus far.

Unverricht-Lundborg Disease

Baltic myoclonic epilepsy.

Increasingly severe myoclonic seizures. Within 5-10 years, symptoms may affect everyday activities such as walking. Tonic-clonic seizures are also common. Decreasing mental function, intention tremors and depression may develop over time. Symptoms manifest in late childhood to early adolescence.

Physical exertion, stress, light, or other stimuli.

Rare.

Caused by mutations in the CSTB gene. Autosomal recessive inheritance.

Generalized to more than one part of the brain.

Life expectancy may be normal depending on the severity of the disorder and the success of treatment.

Sialidosis

Mucolipidosis. Type I, normomorphic sialidosis or cherry-red spot (macular spots) myoclonus syndrome.

This is a lysosomal storage disease. Two types (I and II) distinguished by the age at which symptoms present as well as their severity. Type I present in the teens and twenties with symptoms starting with gait and vision issues progressing to myoclonus, ataxia, tremors and seizures. Myoclonus worsens and eventually requires wheelchair use. Type II is more severe, presents at various points in baby and childhood and is further divided into three types (congenital, infantile, and juvenile)

None specific to sialidosis.

Very rare. Less than 1/1,000,000 is estimated but the true incidence of sialidosis is unknown.

Mutations in the NEU1 gene causes sialidosis. Autosomal recessive inheritance.

Generalized to more than one part of the brain.

Type I has no effect on life expectancy. Congenital type II is often fatal before or shortly after birth. Those with infantile type II survive up to childhood or adolescence. Those with juvenile type II have varying life spans depending on symptoms severity.

Dentatorubral-Pallidoluysian Atrophy (DRPLA)

Haw River syndrome.

Involuntary movements, mental and emotional issues, and decreasing mental ability. Symptoms are more severe if they first appear before age 20 and can appear any time from infancy to mid-adulthood.

None specific to DRPLA.

Unknown worldwide but more commonly found in Japan (1/208,000).

Caused by mutations in the ATN1 gene. Autosomal dominant disorder with worse symptoms when paternally inherited.

Generalized to more than one part of the brain.

Poor. Reduced life expectancy with prognosis depending on the gene mutations present.

Jargon Alert!

Autosomal dominant disorder = only one copy of a defective gene is required for the person to have the disease, disorder or trait.

Reflex epilepsy syndrome.

This form of epilepsy is very broad.  It describes a set of conditions where the common trait is epilepsy caused only by a certain trigger (unless presenting with other forms of epilepsy).  Individuals with only this form of epilepsy will have seizures exclusively provoked by their unique trigger(s). These may external forces such as visual, sensory, auditory, somatosensory or olfactory stimuli and/or internal forces (proprioceptive stimuli, such as certain thought process). Some people may be asymptomatic.

Triggers include flashing lights of a certain frequency, hot water and reading. Unexpected noises or touch may provoke seizures although this is categorized separately as reflex myoclonic epilepsy in infancy (RMEI).

Very rare at only 5% of epilepsy cases.

None that cover all forms of

May be generalized or partial (in more than one or just one part of the brain).

Very good.