Machado-Joseph Disease (Spinocerebellar Ataxia Type 3)

Diagnostic Procedures

Genetic testing revealing CAG repeats are indicative of MJD diagnosis (1). The number of these repeats correlates with severity of the disease; increasing number of repeats corresponds with increased reflexes and mortality rate, and vise versa with decreased number of repeats (2). Type 3 MJD is specifically characterized by fasciculations (3). Health care practitioners must be cautious to rule out amyotrophic lateral sclerolsis (ALS), as the involvement of motor neurons causes the two conditions to present similarly (1).

Upon autopsy, the following findings may be present; encephalon of decreased mass, pale-coloured substantia nigra, atrophied cerebellum, medulla oblongata and pons, as well as a decreased number of neuron bodies in the dentate nucleus, substantia nigra and anterior horn of the spinal cord (1).

Outcome Measures

In order to assess the severity of MJD several scales specific to ataxia can be used. The International Cooperative Ataxia Rating Scale (CARS) and Scale for the Assessment of Rating of Ataxia (SARA) have been shown to be both reliable and effective when used with MJD. (Zhou et al, 2011).

• SARA
• CARS

Common assessment measures that are not specific to MJD but may be useful outcome measures for core symptoms include:

• Berg Balance Scale (BBS),
• Romberg test
• Ashworth scale for spasticity
• Tardieu Scale/Modified Tardieu Scale
• Functional Independence Measure (FIM)
• 6 Minute Walk Test
• Time Up and Go (TUG)
• Psychological General Well-being (PGWB) Index

Differential Diagnosis

The clinical presentation of MJD can often appear like other neurodegenerative diseases that affect movement, the most common differential diagnoses are:

• Parkinson’s Disease
• Multiple Sclerosis (MS)
• Amyotropic Lateral Sclerosis (ALS)