Genomics in general practice

Neurological conditions

Last revised: 30 Nov 2018

Practice point

A small number of adult-onset neurological conditions are due primarily to a single gene mutation (eg Huntington’s disease). There are some more common neurological and neuromuscular conditions that have subsets due to specific gene variants (eg early-onset Alzheimer’s disease and early-onset Parkinson’s disease).1

Positive family history is important in diagnosing neurological conditions with a genetic cause (neurogenetic conditions).2

Relevant history includes:

  • two or more family members affected with the same condition
  • a significantly earlier age of onset than average (ie <50 years old for Parkinson’s disease and <65 years old for Alzheimer’s disease).

There are some neurological conditions that are caused by single gene variants that affect the normal function of muscles and the nervous system (eg neuropathies, myopathies, ataxias). There are also a large number of complex neurological conditions caused by an interplay of genetic and environmental factors.1,3

Many, but not all, paediatric neuromuscular disorders are genetic in nature. These disorders begin in childhood and affect the peripheral nervous system at varying locations.

Although paediatric neuromuscular disorders are rare, the more common ones are:

  • Spinal muscular atrophy: incidence around 1 in 10,000 births4
  • Duchenne muscular dystrophy: incidence around 1 in 5000 male births5
  • Charcot–Marie–Tooth disease: incidence around 1 in 2500 births.6

Genetic studies continue to identify variants that contribute to complex neurological conditions; however, there is currently no role for general practitioners (GPs) in ordering genetic testing for these conditions.

Genetic testing (diagnostic testing and predictive testing) is available through specialist services4 for the following conditions:

  • Creutzfeldt–Jakob disease and other prion diseases
  • early onset Parkinson’s disease
  • familial epilepsy
  • familial motor neurone disease
  • Friedreich ataxia
  • hereditary peripheral neuropathies (Charcot–Marie–Tooth disease)
  • hereditary spastic paraparesis
  • Huntington’s disease
  • mitochondrial disorders
  • muscular dystrophies
  • myotonic dystrophy
  • spinal muscular atrophy
  • spinocerebellar ataxias.

Individuals with suspected neurological conditions should be referred to a neurologist for clinical diagnosis, which may include genetic testing.
Referral to genetics services for predictive genetic testing of asymptomatic family members is appropriate in cases where:

  • there is a proven (clinically or by genetic testing) family history of an inherited neurological or neuromuscular condition
  • there is a suggestive family history as indicated by the presence of
    • two or more family members affected with the same condition
    • a significantly earlier age of onset than average.

Evans-Galea M, Delatycki M, Lockhart P. Explainer: What are neurogenetic diseases? Melbourne: The Conversation, 2014

The RACGP has developed an education activity and other resources for GPs about paediatric neuromuscular disorders and carrier screening here.

  1. Biskup S, Gasser T. Genetic testing in neurological diseases. J Neurol 2012;259(6):1249–54.
  2. Bird TD. Approaches to the patient with neurogenetic disease. Clin Lab Med 2010;30(4):785–93.
  3. Toft M. Advances in genetic diagnosis of neurological disorders. Acta Neurol Scand Suppl 2014(198):20–25.
  4. Darras B. Spinal muscular atrophies. Pediatr Clin N Am 2015;62(3):743–66.
  5. Stark AE. Determinants of the incidence of Duchenne muscular dystrophy. Ann Transl Med 2015;3(19):287. doi: 10.3978/j. issn.2305-5839.2015.10.45.
  6. Silva DL, Palheta Neto FX, Nunes CT, Matos AB, Matos LT, Pacheco A. Otorhinolaryngology clinical features of Charcot–Marie–Tooth disease. Int Arch Otorhinolaryngol 2007;11(4):472–76
  7. The Royal College of Pathologists Australia (RCPA). Genetic tests and laboratories. [Accessed 22 January 2018].
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