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Ohtahara Syndrome

Ohtahara Syndrome



Overview

Ohtahara syndrome is a neurological disorder characterized by seizures.  The disorder affects newborns, usually within the first three months of life (most often within the first 10 days) in the form of epileptic seizures.  Infants have primarily tonic seizures, but may also experience partial seizures, and rarely, myoclonic seizures.  Ohtahara syndrome is most commonly caused by metabolic disorders or structural damage in the brain, although the cause or causes for many cases can’t be determined.  Most infants with the disorder show significant underdevelopment of part or all of the cerebral hemispheres.  The EEGs of infants with Ohtahara syndrome reveal a characteristic pattern of high voltage spike wave discharge followed by little activity.  This pattern is known as “burst suppression.” Doctors have observed that boys are more often affected than girls.

Symptoms

Tonic Seizures: Sudden stiffening of arms/legs, upward gaze, dilated pupils, breathing changes; can be single or clustered, lasting seconds.

Developmental Delays: Significant underdevelopment, failure to meet milestones, intellectual disability.

Low Muscle Tone (Floppiness): Infants often appear very sleepy and floppy.

Other Seizure Types: Focal seizures (affecting one side), or rare myoclonic seizures (sudden jerks).

Feeding Difficulties: Can be associated with poor feeding.

EEG Findings: "Burst suppression" pattern (high-voltage spikes alternating with flat periods). 

Causes

Structural Brain Abnormalities: The most frequent cause, involving malformations like hemimegalencephaly, agenesis of the corpus callosum, or cortical dysplasia.

Genetic Mutations: Mutations in genes critical for brain development and synaptic function, such as STXBP1, ARX, and CDKL5.

Metabolic Disorders: Conditions affecting the body's metabolism, including certain mitochondrial diseases or amino acid disorders. 

Risk Factors

The condition is considered a "final common phenotype" resulting from various severe brain insults, rather than a single disease with standard risk factors. 

Structural Brain Abnormalities

Most cases of Ohtahara syndrome are linked to physical malformations or damage to the brain that occurred during development. These can be diffuse (affecting both sides of the brain) or focal (affecting one specific area). 

Specific examples include:

Cerebral dysgenesis/malformations

Hemimegalencephaly (enlargement of one side of the brain)

Cortical dysplasia (abnormal development of the brain's outer layer)

Porencephaly (cysts or cavities in the brain)

Agenesis of the corpus callosum (absence of the structure connecting the brain hemispheres) 

Related prenatal and perinatal events that can lead to brain damage (and thus increase risk for conditions like OS) include: 

Severe asphyxia (oxygen deprivation during or around birth)

Prematurity

Neonatal sepsis (severe infection in a newborn)

Maternal electric injury during pregnancy 

Genetic Mutations

An increasing number of cases are linked to specific genetic variations that affect brain development or function. These mutations are often spontaneous (de novo), but family history of other epilepsy syndromes may be relevant in some cases. 

Associated genes include:

STXBP1

KCNQ2

SCN2A

ARX

CDKL5 

Metabolic Disorders

Though less common, errors in the body's metabolism can also be a cause. Examples include: 

Non-ketotic hyperglycinemia

Mitochondrial disorders

Pyridoxine-dependent epilepsy 

Complications

Neurological & Developmental Complications

Severe Developmental Delay: Profound cognitive and psychomotor impairment is a hallmark.

Intellectual Disability: Survivors are typically left with severe mental handicaps.

Intractable Seizures: Seizures, often tonic spasms, are very hard to control with medication.

Progression to Other Syndromes: Often evolves into West Syndrome (infantile spasms, hypsarrhythmia) and then Lennox-Gastaut Syndrome (slow spike-waves). 

Physical & Systemic Issues

Feeding Difficulties: Can lead to poor nutrition.

Respiratory Problems: Increased risk of chest infections.

Abnormal Muscle Tone & Movement: May present with spasticity, dystonia, or ataxia.

Microcephaly: May develop in some cases. 

Diagnosis

Clinical Presentation:

Early Onset: Seizures begin in the neonatal period or first few months of life.

Seizure Types: Frequent, brief tonic spasms (muscle stiffening) are hallmark, often occurring in clusters, with possible focal seizures.

Neurological Signs: Developmental delay, intellectual disability, hypotonia (low muscle tone).

Electroencephalogram (EEG):

Burst Suppression: The most crucial diagnostic test, showing bursts of high-amplitude activity followed by periods of flat activity (suppression).

Neuroimaging (MRI):

To identify structural brain abnormalities, common causes include cortical dysplasia, hemimegalencephaly, or other lesions.

Genetic & Metabolic Testing:

Blood/urine tests to rule out treatable metabolic issues (e.g., pyridoxine deficiency).

Genetic tests (like whole exome sequencing) for specific mutations (e.g., STXBP1, ARX). 

Treatment

Medical Treatments

Antiepileptic Drugs (AEDs): Often the first line, but seizures are typically drug-resistant, requiring multiple medications (e.g., Phenobarbitone, Levetiracetam).

Corticosteroids/ACTH: Sometimes used, especially for acute seizure control.

Chloral Hydrate: Has shown success in controlling severe, refractory seizures. 

Dietary Therapies

Ketogenic Diet: A high-fat, low-carb diet that can help control seizures when medications fail. 

Surgical Options (for focal lesions)

Epilepsy Surgery: Removal of a small part (focal resection) or half (hemispherectomy) of the brain if seizures originate from one identifiable, abnormal area, potentially improving development. 

Other Interventions

Vagus Nerve Stimulation (VNS): A device implant can send electrical pulses to reduce seizures in some older children.

Therapies: Physiotherapy, occupational therapy, and speech-language therapy help with motor skills, daily living, and communication. 

Type of Doctor Department : A Pediatric Neurologist


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