to the fastigial nucleus; it receives afferent neuronal supply from the anterior lobe of the cerebellum and sends output via the superior cerebellar peduncle and the red nucleus. The fastigial nucleus is the most medial efferent cerebellar nucleus, targeting the pontine and medullary reticular formation as well as the vestibular nuclei. This region deals with antigravity muscle groups and other synergies involved with standing and walking. It is thought that fastigial nuclei axons are excitatory and project beyond the cerebellum, likely using glutamate and aspartate as neurotransmitters. Pathology Malformations of the posterior fossa have been recognized more frequently during the past few decades as the result of recent advances in technology. Malformations of the cerebellar vermis were first identified using pneumoencephalography, where air is injected into the cerebrospinal fluid spaces of the cerebellum; displaced, occluded or dysplastic structures could be identified. Upon the advent of computerized tomography (CT) and magnetic resonance imaging (MRI), the resolution of cranial structures including the mid-hindbrain regions improved dramatically. Joubert syndrome Joubert syndrome (JS) is one of the most commonly diagnosed syndromes associated with the molar tooth sign (MTS), or hypoplasia/dysplasia of the cerebellar vermis accompanied by brainstem abnormalities. JS is defined clinically by features of hypotonia in infancy with later development of ataxia, developmental delays, mental retardation, abnormal breathing patterns, abnormal eye movements specific to oculomotor apraxia, or the presence of the MTS on the cranial MRI. JS is an autosomal recessive condition with an estimated prevalence of 1: 100,000. Dandy Walker malformation Dandy Walker malformation is a relatively common congenital brain malformation with a prevalence of 1:30,000 live births. Dandy Walker malformation is characterized by enlarged posterior fossa and in which the cerebellar vermis is completely absent, or present in a rudimentary form, sometimes rotated accompanied by an elevation of the fourth ventricle. It is also commonly associated with dysplasias of brainstem nuclei. DWM has been reported to be in association with a wide array of chromosomal anomalies, including trisomy 18, trisomy 9, and trisomy 13. Surveys suggest that prenatal exposure to teratogens such as rubella or alcohol are correlated with development of Dandy Walker malformation. Rhombencephalosynapsis Rhombencephalosynapsis is an anomaly characterized by the absence or severe dysgenesis of the cerebellar vermis with fusion of the cerebellar hemispheres, peduncles, and dentate nuclei. Diagnostic features include fusion of the midbrain colliculi, hydrocephalus, absence of the corpus callosum other midline structural brain malformations. Damage Lesions