Which cerebellar disease is associated with hypertonia?

Cerebellar Disease Associated with Hypertonia

Hepatic myelopathy (HM) is the cerebellar-related disease most characteristically associated with hypertonia, presenting with severe motor abnormalities including progressive spasticity, weakness of lower limbs, and hyper-reflexia that exceed mental dysfunction. 1

Primary Cerebellar Conditions with Hypertonia

Hepatic Myelopathy

• Hepatic myelopathy represents a particular pattern of hepatic encephalopathy related to marked, long-standing porto-caval shunting, characterized by severe motor abnormalities that exceed mental dysfunction. 1
• Cases present with paraplegia, progressive spasticity and weakness of lower limbs with hyper-reflexia, and relatively mild persistent or recurrent mental alterations. 1
• This condition does not respond to standard ammonia-lowering therapy but may reverse with liver transplantation. 1
• The American Association for the Study of Liver Diseases notes that motor system abnormalities in hepatic encephalopathy, including hypertonia, hyper-reflexia, and positive Babinski sign, can be observed in noncomatose patients. 1

Williams Syndrome

• Williams syndrome presents with a distinctive pattern of axial hypotonia combined with peripheral hypertonia and increased deep tendon reflexes in the lower extremities. 1
• Signs of cerebellar dysfunction, such as ataxia and tremor, may increase with age in these patients. 1
• Posterior fossa size is reduced in Williams syndrome, although cerebellar volume is preserved, which may contribute to Chiari I malformation in some individuals. 1

Infantile-Onset Syndromic Cerebellar Ataxia (CACNA1G mutations)

• Gain-of-function mutations in CACNA1G cause infantile-onset cerebellar ataxia with hypertonia as a prominent feature, along with cerebellar atrophy or hypoplasia, psychomotor delay, and severe intellectual disability. 2
• This represents a homogeneous neurodevelopmental syndromic disorder with distinctive dysmorphic and ectodermal features. 2

Important Clinical Distinctions

Typical Cerebellar Syndromes vs. Hypertonic Variants

• Classic cerebellar syndromes typically present with hypotonia or normal muscle tone, not hypertonia. 3, 4
• The presence of hypertonia in a cerebellar disorder should prompt consideration of specific entities like hepatic myelopathy, Williams syndrome, or genetic syndromes with mixed upper motor neuron and cerebellar features. 1, 2

Pathophysiologic Considerations

• Hypertonia in cerebellar disease contexts typically reflects loss of supraspinal control mechanisms or network dysfunction between basal ganglia and thalamo-cerebello-cortical connections, rather than pure cerebellar pathology. 5
• The combination of cerebellar signs with hypertonia suggests involvement of multiple neural pathways beyond isolated cerebellar dysfunction. 5

Clinical Pitfalls to Avoid

• Do not assume all cerebellar diseases present with hypotonia—specific entities like hepatic myelopathy and Williams syndrome characteristically demonstrate hypertonia. 1
• When evaluating a patient with both cerebellar signs and hypertonia, systematically assess for hepatic dysfunction, genetic syndromes, and mixed upper motor neuron involvement. 1, 2
• In hepatic encephalopathy patients, recognize that mental and motor signs may not progress in parallel, making staging difficult. 1