Progressive Ataxia and Palatal Tremor

Progressive ataxia and palatal tremor is a syndrome of slowly progressive cerebellar ataxia together with rhythmic palatal movements, usually from degeneration of the dentato-rubro-olivary circuit. It can be sporadic or genetic.

It is rare, and onset is usually in middle age (30 to 60 years).

Palatal tremor types. Symptomatic palatal tremor follows a brainstem or cerebellar lesion and is linked to hypertrophic olivary degeneration. Essential palatal tremor causes an ear click, with no neurological disease. Progressive ataxia and palatal tremor is a distinct degenerative form.

Genetic causes. Adult onset Alexander disease (GFAP variants, with prominent medulla and cervical cord atrophy), POLG-related disease, spinocerebellar ataxia type 20, and other mitochondrial disease. Many sporadic cases have no identified cause.

Pathophysiology. Hypertrophic olivary degeneration follows disruption of the Guillain-Mollaret triangle (dentate nucleus, red nucleus and inferior olive), producing synchronised inferior olive oscillation.

Presentation is gait and limb ataxia, dysarthria and dysphagia, with continuous 1 to 3 Hz rhythmic movement of the soft palate, sometimes with oscillopsia, pendular nystagmus, ocular bobbing, limb tremor, myoclonus, spasticity, bulbar signs and, in some, cognitive change. Ear click suggests tensor veli palatini involvement.

MRI brain and cervical cord (hypertrophic olivary degeneration on T2 with inferior olive enlargement and hyperintensity, cerebellar and medullary atrophy, and signal change in the brainstem). Genetic testing for GFAP, POLG, SCA20 and a wider ataxia panel. Check lactate, thyroid function, vitamin B12, E and copper, and anti-GAD antibodies. Electromyography of palatal muscles is rarely needed.

Differential diagnosis.

• Secondary palatal tremor from brainstem stroke, tumour, demyelination or trauma.
• Multiple system atrophy, spinocerebellar ataxias and Alexander disease.
• Mitochondrial disease, autoimmune cerebellar ataxia and Wilson disease.

There is no disease modifying treatment. Care is symptomatic.

Palatal tremor and ear click. Botulinum toxin injected into the tensor veli palatini or palatal muscles, using the dose in the product label, under experienced direction. Clonazepam 0.5 mg at night, increased to 4 mg daily in divided doses, may help tremor and oscillopsia. Monitor sedation, falls and dependence.

Ocular symptoms. Gabapentin 300 mg three times daily, increased to 1800 mg daily (adjust to eGFR), or memantine 5 mg daily increased to 20 mg daily (reduce in renal impairment), for oscillopsia and nystagmus.

Ataxia and other signs. Physiotherapy, occupational therapy, speech and swallowing therapy, falls prevention, and gait aids.

Treat the cause. Control the underlying vascular, inflammatory or other lesion when identified. For genetic forms, provide genetic counselling.

Monitoring. Ataxia scale, swallowing and function every 6 to 12 months.

Referral and escalation. Refer to neurology and clinical genetics.

Special groups. In mitochondrial disease, avoid valproate and drugs that impair mitochondrial function.