Dysfunction of the autonomic nervous system is an under-recognised but important aspect of the aetiological and clinical manifestation of primary degenerative
dysautonomias such as
multiple system atrophy (MSA) and
Parkinson's disease (PD). Although the clinical presentation of
dysautonomia in these two disorders may overlap, yet pathological and in vivo imaging studies suggest considerable differences. Functional imaging studies suggest that selective cardiac
sympathetic denervation may occur early in PD but not in other
parkinsonian syndromes. The clinical implication of this apparently disease specific peripheral
dysautonomia is unknown and would be the subject of much interest in future years.
Dysautonomia in degenerative disorders also affect respiration, genitourinary function and sleep. Sleep related disorders such as rapid eye movement behaviour disorder and urinary voiding dysfunction appear to precede the development of PD related symptoms while patients with sporadic
ataxia have been shown to progress to develop MSA.
Dysautonomia has also been recognised in other
movement disorders, examples being the combination of
dystonia and
complex regional pain syndrome with elevated
HLA-DR13 and late onset
Huntington's disease presenting with dominant
parkinsonism and minimal
chorea. These studies have helped progress in various diagnostic and management parameters in relation to autonomic dysfunction and
movement disorders.