Ocular motor apraxia is a rare congenital disorder characterized by a defect in side-to-side (horizontal) eye movements. The eyes do not move properly in response to stimuli or voluntarily. When affected infants are asked to fixate on an object to the side, their eyes will lag and then move in the opposite direction. In order to compensate for this, the infants will sharply jerk their heads past the desired object in an effort to bring the eyes to a position where they can view the object. When the eyes fixate on the object, the head will return to its normal position. These jerking head movements are the most noticeable sign of Cogan type ocular motor apraxia and are usually recognized three to four months after birth. Before these head jerkings occur, an infant's inability to fixate on an object may sometimes be mistaken for blindness.
Infants with Cogan type ocular motor apraxia will also be unable to follow rapid movements across their fields of vision, such as focusing on a moving train (opticokinetic nystagmus). The disorder can also be associated with mild developmental delay and speech difficulties.
In other rare cases of Cogan type ocular motor apraxia, individuals exhibit an inability to fixate on objects to one particular side of the body (unilateral ocular motor apraxia). In some of these cases, individuals may demonstrate improper eye movements and/or an inability to track an object with the other eye.
Cogan type ocular motor apraxia is not progressive and many affected individuals eventually learn to compensate for the disorder by overshooting the eyes instead of jerking the head. The number and severity of symptoms varies widely among affected individuals.
Some individuals with Cogan type ocular motor apraxia have a brain abnormality such as underdevelopment (hypoplasia) of the corpus callosum, hypoplasia of the cerebellum, or an abnormality in the grey matter. (For more information on agenesis of corpus callosum, see the Related Disorders section of this report.)
Other Related Conditions
Symptoms of the following disorders can be similar to those of Cogan type ocular motor apraxia. Comparisons may be useful for a differential diagnosis:
Jouberts Syndrome is characterized by absence or underdevelopment of the cereberllar vermis and a malformed brain stem (molar tooth sign). The most common features include ataxia (lack of muscle control), hyperpnea (abnormal breathing patterns), sleep apnea, abnormal eye and tongue movements, and hypotonia. Other malformations such as extra fingers and toes, cleft lip or palate, tongue abnormalities, and seizures may also occur. There may be mild or moderate retardation. Joubert syndrome is one of the many genetic syndromes associated with syndromic retinitis pigmentosa.Provided by:http://en.wikipedia.org/wiki/Joubert_syndrome
Balint's Syndrome is a rare eye disorder characterized by the inability to voluntarily look at objects to the side (peripherally). An affected individual may also have trouble grasping objects due to difficulties with hand-to-eye coordination and may be unable to follow objects across the eyes' field of vision. Although the exact cause of Balint's syndrome is not known, it is thought that symptoms may be caused by improper development of part of the brain.
Ataxia-Telangiectasia is a rare inherited form of cerebellar ataxia that usually begins during infancy. It is characterized by loss of coordination of the limbs, the head, and the eyes, and a lower than normal immune response against infections. Rapid eye blinking, abnormal eye movements, and head thrusting may develop gradually. Ataxia-telangiectasia may be confused with Cogan type ocular motor apraxia prior to the development of visible widened (dilated) blood vessels (telangiectasias). However, unlike individuals with Cogan type ocular motor apraxia, individuals with ataxia-telangiectasia have defective up-and-down (vertical) as well as side-to-side (horizontal) eye movements. Ocular telangiectasias, which lead to a bloodshot appearance, usually begin between three and six years of age but may occur earlier. Ataxia-telangiectasia is inherited as an autosomal recessive genetic trait.
The following disorder may precede the development of Cogan type ocular motor apraxia. It can be useful in identifying an underlying cause of some forms of this disorder:
Agenesis of Corpus Callosum (ACC) is a rare neurological disorder that is present at birth (congenital). It is characterized by a partial or complete absence (agenesis) of the area of the brain that connects the two cerebral hemispheres. Symptoms of this disorder include seizures and delays in the ability to properly sit, stand, or walk (developmental delays). Agenesis of corpus callosum is usually inherited as either an autosomal recessive trait or an X-linked dominant trait.