About vermis cerebellar agenesis
What is vermis cerebellar agenesis?
Joubert syndrome is an autosomal recessive genetic disorder that affects the area of the brain that controls balance and coordination. This condition is characterized by a specific finding on an MRI called a "molar tooth sign" in which the cerebellar vermis of the brain is absent or underdeveloped and the brain stem is abnormal. The most common features of Joubert syndrome are lack of muscle control (ataxia), abnormal breathing patterns (hyperpnea), sleep apnea, abnormal eye and tongue movements and low muscle tone.
What are the symptoms for vermis cerebellar agenesis?
The signs and symptoms of cerebellar agenesis can vary greatly from one individual to another. According to the medical literature, some individuals with cerebellar agenesis have had only mild symptoms. In fact, in some reported cases, it has been claimed that motor function may be almost normal, perhaps due to partial compensation from other areas of the brain. Reports in the medical literature discuss individuals with cerebellar agenesis who had a normal lifespan, attended regular schools and found employment and lived productive though often “simple” lives.
Additional reports have noted individuals with cerebellar agenesis whose mental capacities were unaffected and who did not exhibit any symptoms of cerebellar agenesis (asymptomatic cases). However, other researchers have disputed these claims, stating that in virtually all of cases of cerebellar agenesis there have been observable symptoms including profound abnormalities in motor skills. Most likely, cerebellar agenesis represents a spectrum of disease that may range from those with severe disability to those with milder expressions of the disorder.
It is important to note that the symptoms of cerebellar agenesis are extremely variable and that affected individuals may not have all of the symptoms discussed below. Affected individuals or parents of affected children should talk to their physician and medical team about their specific case, associated symptoms and overall prognosis.
Cerebellar agenesis is most often associated with impairment of motor function, especially an inability to coordinate of voluntary movements (ataxia). Affected individuals may be clumsy and there may be delays in the acquisition of motor activities (psychomotor delays). Walking may be delayed until 4-7 years of age. Cerebellar agenesis may also be associated with Low muscle tone (hypotonia).
Some affected individuals may have difficulty speaking usually due to problems with the muscles that enable speech (dysarthria). The ability to speak is usually delayed, sometimes significantly. Some individuals may exhibit rapid, involuntary movements of the eyes (nystagmus).
Intelligence may be unaffected. However, some affected individuals may display mild to moderate cognitive impairment. Some individuals with cerebellar agenesis have exhibited intellectual disability, but normal or near-normal motor skills.
In addition to affecting motor skills, damage to the cerebellum has also been associated with abnormalities of non-motor functions. Cerebellar dysfunction may also be associated with abnormalities of visuospatial abilities, expressive language, working memory and affective behavior.
What are the causes for vermis cerebellar agenesis?
The etiology of cerebellar agenesis is not uniform, but varied (heterogeneous). Acquired (prenatal/perinatal) causes include cerebellar destruction caused by hemorrhage, lack of or diminished blood flow (ischemia), or other factors. This has been documented in a minority of children with spina bifida (myelomeningocele), also called “vanishing cerebellum in myelomeningocele”. It is being increasingly recognized in premature babies with very low birth weight (also called “cerebellar disruption of prematurity”), and is often accompanied by additional anomalies of the brain.
The exact cause of isolated cerebellar agenesis often remains unknown. Most cases occur randomly for unknown reasons (sporadically).
A genetic cause is only documented in an extremely rare syndrome of cerebellar agenesis and agenesis of the pancreas, resulting in neonatal diabetes mellitus. This syndrome is caused by mutations in the PTF1A gene, and it is inherited in an autosomal recessive manner.
What are the treatments for vermis cerebellar agenesis?
The treatment of cerebellar agenesis is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists. Pediatricians, neurologists, speech pathologists, and other healthcare professionals may need to systematically and comprehensively plan an affected child’s treatment.
Early intervention is important in ensuring that children with cerebellar abnormalities reach their highest potential. Services that may be beneficial may include physical therapy, occupational therapy and speech therapy. In some children, special remedial education may be of benefit. Adaptive devices may assist individuals with significant motor deficits or speech difficulties.
What are the risk factors for vermis cerebellar agenesis?
Cerebellar agenesis appears to affect males and females in equal numbers. The exact incidence and prevalence of the disorder in the general population is unknown. Congenital isolated cerebellar agenesis is considered an extremely rare occurrence.