Oculomotor Apraxia
Patient Information
Characteristics
Background and History
Abnormal eye movements are often part of other, more generalized, neurological disorders. However, rare individuals may have such symptoms without other health problems as in this disorder
Clinical Correlations
This condition may be apparent shortly after birth when it is evident that infants are unable to turn their eyes appropriately to look at targets. The deficit is almost entirely in horizontal gaze and most children are able to look up and down without difficulty. Most youngsters learn quickly to turn their head instead but do so in a halting, jerky fashion. The condition is not progressive and, in fact, many older individuals actually have less difficulty moving their eyes suggesting that there can be some improvement.
In most cases there are no other health problems but mild developmental delay or speech difficulties have been reported in a few patients.
Genetics
Inheritance
The genetics of oculomotor apraxia are murky since no responsible gene mutation has been identified. Familial cases, including twins, have been reported some of whom were offspring of consanguineous (related) parents suggesting autosomal recessive inheritance. However, other families have been seen in which cases occurred in multiple generations suggesting autosomal dominant inheritance. Most likely several disorders are represented.
Oculomotor apraxia may also be seen in neurological syndromes, most commonly when a part of the brain known as the cerebellum is improperly developed.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
The diagnosis is usually made by a neurologist or by an ophthalmologist who has ruled out other eye disease based on an eye examination. The prognosis is excellent and many patients actually improve.
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