What is Ocular Motor Apraxia?

By Aimee MolineuxReviewed by Emily Henderson, B.Sc.

Introduction
History
Cause and types
Symptoms
Epidemiology
Ataxia with oculomotor apraxia
Diagnosis and treatment
References
Further reading

Ocular motor apraxia (OMA) is a neurological condition resulting in an inability to turn the eyes voluntarily in a horizontal manner. Ocular Motor Apraxia is known by a variety of terms. OMA is sometimes referred to as Cogan's Ocular Motor Apraxia (COMA) or Saccadic Initiation Failure (SIF).

Children with OMA often encounter trouble focusing their eyes on an object or monitoring a moving object. OMA may be present from birth (congenital), and the symptoms appear in childhood. OMA can also develop after birth in some cases. Congenital ocular motor apraxia (also known as infantile-onset saccade start delay or ISID) and acquired ocular motor apraxia are two types of ocular motor apraxia.

History

Cogan first documented four children in 1952 who could only change their gaze direction quickly by doing horizontal head thrusts. Using the vestibuloocular reflex, the eyes moved contralateral to the direction of head movement until they reached the orbit's extreme position during the head thrusts. During the head thrust, the eyes were drawn to the desired location. He coined the term "ocular motor apraxia" to describe this symptom. Since then, several single cases or case series associated with OMA have been published in the medical literature.

Cause and types

OMA can be an independent condition, have a hereditary component, or be linked to other syndromes. The Cogan-type of idiopathic congenital OMA is commonly accompanied by developmental delay. It can also develop later in life and is referred to as acquired OMA. OMA has been found in a variety of clinical disorders, including metabolic and neurological diseases. Ataxia with oculomotor apraxia, ataxia-telangiectasia, Gaucher's disease, and Joubert syndrome are a few examples.

According to scientists, the core cause of this condition could be hereditary, although no single gene or genes have been identified as the cause. Some scientists believe that OMA is caused in some cases by a disorder or incident that disrupts normal brain development during pregnancy. Perinatal hypoxia, cerebral palsy, anemia, convulsions, and meningitis are some possible causes of OMA.

Symptoms

Along with difficulties associated with eye movement, children may also experience low muscle tone, learning difficulties, and delays in language development. Delay in sitting, walking, and toilet training has also been observed.

Since some infants with ISID do not appear to visually follow a moving huge object, they are initially misdiagnosed as blind. Horizontal head thrusts become apparent as head control develops, usually around 4–6 months of age. In typically developing children, the frequency of head movements decreases as they get older during gaze transitions.

Early-onset OMA, along with infantile muscular hypotonia, early-onset ataxia, and newborn respiratory problems, is a common sign of Joubert syndrome (JBTS). There is also evidence of episodic tachypnea and apnea, as well as developmental delay and intellectual disabilities.

Vertical saccade involvement, nystagmus, and developmental abnormalities are linked to non-idiopathic OMA. Endocrine abnormalities may also be more common in OMA children than in the overall pediatric population.

Epidemiology

Males are affected twice as often as females by Cogan-type ocular motor apraxia. By the third or fourth month of birth, the jerking head motions associated with this disease have usually appeared. In the medical literature, about 50 cases have been reported. Only a few examples of acquired OMA have been documented in the medical literature. 

Related: What Causes Ocular Hypertension?

Ataxia with oculomotor apraxia

The condition ataxia with oculomotor apraxia is characterized by movement impairments that increase with time. Poor coordination and balance, often known as ataxia, is the most common sign of this condition. The majority of those affected also have oculomotor apraxia. There are various forms of ataxia with oculomotor apraxia, with types 1, 2, and 4 being the most frequent. The types are quite similar, however, they are caused by different gene mutations.

Around the age of four, type 1 begins. Affected individuals may experience chorea or myoclonus in addition to ataxia and oculomotor apraxia. Type 1 patients have lower quantities of albumin, which leads to higher cholesterol levels. Oculomotor apraxia type 2 ataxia usually occurs around the age of 15. Chorea or myoclonus can occur in people with type 2, and these movement problems can last a lifetime. This type is also prone to neuropathy. Around the age of four, ataxia with oculomotor apraxia type 4 develops. Individuals with this type often develop dystonia in addition to ataxia and oculomotor apraxia.

Diagnosis and treatment

Early signs of OMA may go unnoticed or be mistaken for vision issues. Since the disorder is rare, many doctors may be unfamiliar with its symptoms. As a result, there is considerable potential for misdiagnosis. An eye doctor can confirm the diagnosis by examining the child's eye movements. To rule out other probable causes of the symptoms, physical and neurological testing is performed. Ophthalmological exams can rule out any eye disorders that could be causing the symptoms. Brain abnormalities that are occasionally related to OMA can be found with an MRI or CT scan.

OMA does not have a specific treatment. However, physical, occupational, and speech therapy can benefit the patients. The therapy of OMA that is caused by an underlying condition should be focused on that disorder. Regular ophthalmologic exams are advised to keep track of any additional eye disorders that may be linked to OMA.

References

1. Chang, M. Y., Grosrenaud, P., & Borchert, M. S. (2022). Characteristics and Outcomes of Idiopathic and Non-idiopathic Ocular Motor Apraxia in Children. Journal of pediatric ophthalmology and strabismus, 1–6. Advance online publication. https://doi.org/10.3928/01913913-20220106-01
2. Tilikete, C., & Robert, M. P. (2019). Ocular Motor Apraxia. In Advances in Translational Neuroscience of Eye Movement Disorders (pp. 451-470). Springer, Cham. https://doi.org/10.1007/978-3-030-31407-1_22
3. Wente, S., Schröder, S., Buckard, J., Büttel, H. M., von Deimling, F., Diener, W., Häussler, M., Hübschle, S., Kinder, S., Kurlemann, G., Kretzschmar, C., Lingen, M., Maroske, W., Mundt, D., Sánchez-Albisua, I., Seeger, J., Toelle, S. P., Boltshauser, E., & Brockmann, K. (2016). Nosological delineation of congenital ocular motor apraxia type Cogan: an observational study. Orphanet journal of rare diseases, 11(1), 104. https://doi.org/10.1186/s13023-016-0486-z
4. Salman M. S. (2015). Infantile-onset saccade initiation delay (congenital ocular motor apraxia). Current neurology and neuroscience reports, 15(5), 24. https://doi.org/10.1007/s11910-015-0543-3
5. Chen, J. J.; Thurtell, M. J. (2012). Acquired ocular motor apraxia due to bifrontal haemorrhages. Journal of Neurology, Neurosurgery & Psychiatry, 83(11), 1117–1118. doi:10.1136/jnnp-2012-303405
6. OCULAR MOTOR APRAXIA. [Online] OMIM. Available at: https://www.omim.org/entry/257550#
7. Ocular Motor Apraxia. [Online] United brain association. Available at: https://unitedbrainassociation.org/brain-resources/ocular-motor-apraxia/
8. Oculomotor Apraxia. [Online] America association for pediatric ophthalmology and strabismus. Available at: https://aapos.org/glossary/oculomotor-apraxia#
9. Ataxia with oculomotor apraxia. [Online] Medline Plus. Available at: https://medlineplus.gov/genetics/condition/ataxia-with-oculomotor-apraxia/
10. Medical Information on Ocular Motor Apraxia. [Online] Scottish sensory centre. Available at: https://www.ssc.education.ed.ac.uk/
11. Ocular Motor Apraxia, Cogan Type. [Online] National organization for rare disorders. Available at:  https://rarediseases.org/rare-diseases/ocular-motor-apraxia-cogan-type/

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