Cerebellar hypoplasia is characterized by reduced

cerebellar The cerebellum (Latin for "little brain") is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as or even larger. In humans, the cereb ...

volume, even though cerebellar shape is (near) normal. It consists of a heterogeneous group of disorders of

maldevelopment presenting as early-onset non–progressive congenital ataxia,

hypotonia Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases ...

and motor learning disability. Various causes have been incriminated, including hereditary, metabolic,

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

and viral agents. It was first reported by French neurologist Octave Crouzon in 1929. In 1940, an unclaimed body came for dissection in

London Hospital The Royal London Hospital is a large teaching hospital in Whitechapel in the London Borough of Tower Hamlets. It is part of Barts Health NHS Trust. It provides district general hospital services for the City of London and Tower Hamlets and sp ...

and was discovered to have no cerebellum. This unique case was appropriately named "human brain without a cerebellum" and was used every year in the Department of Anatomy at

Cambridge University The University of Cambridge is a Public university, public collegiate university, collegiate research university in Cambridge, England. Founded in 1209 and granted a royal charter by Henry III of England, Henry III in 1231, Cambridge is the world' ...

in a neuroscience course for medical students. Cerebellar hypoplasia can sometimes present alongside hypoplasia of the corpus callosum or

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

. It can also be associated with

hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary inc ...

or an enlarged

fourth ventricle The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ve ...

; this is called

Dandy–Walker malformation Dandy–Walker malformation (DWM), also known as Dandy–Walker syndrome (DWS), is a rare congenital brain malformation in which the part joining the two hemispheres of the cerebellum (the cerebellar vermis) does not fully form, and the fourth ...

Signs and symptoms

Non-progressive early onset

ataxia Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements that can include gait abnormality, speech changes, and abnormalities in eye movements. Ataxia is a clinical manifestation indicating dysfunction of ...

and poor motor learning are the most common presentation.

Diagnosis

Magnetic resonance imaging

Three dimensional (3D) T2-weighted (T2w), axial, coronal,

sagittal The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divi ...

magnetic resonance imaging (MRI) is considered appropriate for differentiation between gray matter and white matter acquisition of high-resolution anatomic information. T2w, axial and coronal imaging is more suitable for acquisition of high-resolution anatomic information and delineation of cortex, white matter, and gray matter nuclei. Diffusion tensor, axial imaging is used for evaluation of white matter microstructural integrity, identification of white matter tracts. CISS, axial + MPR imaging for evaluation of cerebellar folia, cranial nerves, ventricles, and foramina. Susceptibility weighted axial scans are employed for identification and characterization of hemorrhage, blood products, calcification, and iron accumulation.

Classification

Classification systems for malformations of the cerebellum are varied and are constantly being revised as greater understanding of the underlying genetics and embryology of the disorders is uncovered. A classification proposed by Patel S in 2002 divides cerebellar malformations in two broad groups; those with cerebellar hypoplasia and; those with cerebellar dysplasia. * I. Cerebellar hypoplasia ** A. Focal hypoplasia *** 1. Isolated vermis *** 2. One hemisphere hypoplasia ** B. Generalized hypoplasia *** 1. With enlarged fourth ventricle (“cyst,”), Dandy–Walker continuum *** 2. Normal fourth ventricle (no “cyst”) **** a. With normal pons **** b. With small pons i. Normal foliation ***** a) Pontocerebellar hypoplasias of Barth, types I and II ***** b) Cerebellar hypoplasias, not otherwise specified

Treatment

There is no standard course of treatment for cerebellar hypoplasia. Treatment depends upon the underlying disorder and the severity of symptoms. Generally, treatment is symptomatic and supportive. Balance rehabilitation techniques may benefit those experiencing difficulty with balance. Therapies include physical, occupational, speech/language, visual, psychiatric/behavioral meds, and special education.

Prognosis

The prognosis of this developmental disorder is highly based on the underlying disorder. Cerebellar hypoplasia may be progressive or static in nature. Some cerebellar hypoplasia resulting from congenital brain abnormalities/malformations are not progressive. Progressive cerebellar hypoplasia is known for having poor prognosis, but in cases where this disorder is static, prognosis is better.

History

Following clinical report by Crouzon in 1929 Sarrouy reported two pairs of siblings with congenital cerebellar hypoplasia in 1958. However pons, pyramidal tract and corpus callosum were also involved in these cases. Wichman et al. in 1985 reported three sibling pairs with congenital cerebellar hypoplasia. "All six children presented in the first years of life with delays in motor and language development. All patients showed cerebellar and/or vermal dysfunction and, on formal psychometric testing, cognitive abilities ranged from normal to moderately retarded. Abnormalities on CT scan ranged from prominent valleculla to an enlarged cisterna magna with hypoplasia of the cerebellar hemispheres and vermis. The pedigrees are consistent with autosomal recessive inheritance." Mathews KD, in 1989 also reported two cases of cerebellar hypoplasia in a family with unaffected parents suggestive of autosomal recessive inheritance. The frequency and importance of the evaluation of the posterior fossa have increased significantly over the past 20 years owing to advances in neuroimaging with frequent reporting of posterior fossa malformation.

References

External links

* * {{DEFAULTSORT:Cerebellar Hypoplasia Congenital disorders of nervous system Genetic disorders with no OMIM Systemic atrophies primarily affecting the central nervous system