Alternating Hemiplegia of Childhood (AHC)

AHC is a rare neurological syndrome. 'AHC' means Alternating Hemiplegia of Childhood.
Temporary paralysis symptoms occur on one or both sides of the affected child's body.

The paralysis can change between half of the body and lasts from a few minutes to a few days. This syndrome also includes noticeable eye movements.

The first symptoms can appear before the age of 18 months. Muscle tension disorders (dystonia) or half-sided paralysis (hemiparesis) can occur in the first six months of life. Abnormal eye movements in the first three months of life.

 

Characteristics of AHC

• temporary paralysis
  • of arm or leg
  • of one half of the body (half-sided paralysis) or half-sided loss of strength (hemiparesis)
  • of both halves of the body
• recurring paralysis
• short-term paralysis lasting minutes to days
• sudden paralysis
• paralysis disappears when the child sleeps and returns upon awakening
• reduced consciousness
• not being able to talk, eat or drink
• muscle cramps
• breathing disorders
• pain

 

Neurological abnormalities during a paralysis attack or in the period between the paralysis attack

• attacks with abnormal movements possible with
  • stiffening of muscles of the arm and/or leg
  • dystonia (muscle tension disorder with abnormal position of and/arm or leg)
  • chorea (twisting movement of arm and/or leg as in a dance)
    athetosis (jerking movement of arm and/or leg)
  • ataxia
• paroxysmal (seizure) temporary abnormal eye movement (nystagmus, convulsions and/or squinting)
• disruption of autonomic functions:
  • breathing problems: breathing too fast or too slow
  • attacks of altered heart rhythm: too fast or too slow heart rate
  • pale look

These symptoms do not occur in every child.

 

Possible consequences

• epileptic seizures (often independent of the paralysis attack)

• emotion and behavioral problems
  
  • irritable behavior
  • mood swings (can be a precursor to an attack)
  • difficulty with frustration
  • fears
  • burst into tears easily
• permanent or permanent failure symptoms
• increasing balance problems

 

Progress and development

It is reported that children with AHC have disturbed development, which comes to a standstill and even deterioration of skills already learned.
Increasing balance problems are reported.
Cognition, speech, motor skills and social interaction may be permanently disturbed.
The AHC attacks may decrease or change in duration and frequency as the child grows older. Not every child becomes seizure-free. The symptoms of failure can be permanent.
Life expectancy is in principle normal unless complications shorten life expectancy.

 

Factors that can provoke an attack

NB! Attacks cannot be prevented by avoiding triggers. They can also occur without a trigger.

• extreme temperature differences/changes in temperature, including when taking a bath or swimming, cold
• increased physical activity
• sensory stimulation such as:
  • light
  • odor
• fatigue
• medication
• nutrients: dyes, chocolate

 

Cause of AHC

A mutation in the ATP1A3 gene is the cause of AHC in 70% of cases.

It is transmitted autosomally, i.e. by one of both parents. ATP1A3 stands for ATPase, Na+K+ transporting, alpha 3 polypeptide. AHC patients with epilepsy have a greater chance of having the specific gene mutation than people without epilepsy.

The ATP1A3 isoform is only expressed in neurons of brain regions such as the basal ganglia, hippocampus and cerebellum.

 

Other names for AHC

• AT1A3_HUMAN
• ATPase, Na+/K+ transport, alpha 3 polypeptide
• DYT12
• MGC13276
• Na+/K+ ATPase 3
• Na+/K+ -ATPase alpha 3 subunit
• RDP
• sodium potassium ATPase, alpha 3 polypeptide
• sodium pump 3
• sodium/potassium-transporting ATPase alpha-3 chain

 

More information

The AHC foundation

The Dutch AHC association also has more information on this subject. They are also strongly committed to the need for more scientific research that requires money. https://www.ahckids.nl/over-ahc