Oculogyric crises are a characteristic symptom of aromatic L‐amino acid decarboxylase (AADC) deficiency, a neuromuscular condition caused by a mutation in the dopa decarboxylase (DDC) gene.
What are oculogyric crises?
Oculogyric crises are eye movement disorders in which the gaze is involuntarily fixed upward due to spasms in the eye muscles that support eye movement.
Patients are unable to move their eyes away during oculogyric crises.
Oculogyric crises are usually accompanied by an open mouth, protruding tongue, restricted neck movement, and lip-smacking.
Oculogyric crises can last for minutes in the early stages of AADC deficiency. However, as the condition progresses, these episodes may last for hours.
Anxiety and emotional outbursts often accompany oculogyric crises. The duration and accompanying symptoms are patient-specific and may vary from episode to episode.
How does AADC deficiency lead to oculogyric crises?
The underlying cause of oculogyric crises in AADC deficiency is unclear. However, it has frequently been linked to decreased levels of the neurotransmitter dopamine. The AADC enzyme is essential for the synthesis of dopamine.
In AADC deficiency, a mutation in the DDC gene leads to insufficient production of the AADC enzyme, which in turn affects the production of dopamine and may trigger oculogyric crises.
One of the main functions of dopamine is to relay nervous signals from the brain to the rest of the body. Dopamine also regulates several eye functions, such as response to light, visual communication, eye development, and muscle coordination. Therefore, an imbalance in dopamine levels may lead to eye problems, including oculogyric crises.
Oculogyric crises have been reported in other neurometabolic conditions like tyrosine hydroxylase deficiency, Wilson’s disease, and Parkinson’s disease. They can also be triggered by neuroleptic or antipsychotic medications.
Last updated: Sept. 17, 2019.
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