Can cerebellar ataxia cause loss of sphincter control, leading to urinary or fecal incontinence?

Can Cerebellar Ataxia Cause Loss of Sphincter Control?

Pure cerebellar ataxia alone does not typically cause loss of sphincter control; however, when sphincter dysfunction occurs alongside cerebellar ataxia, it strongly suggests a diagnosis other than isolated cerebellar disease—most notably Multiple System Atrophy (MSA) or other conditions affecting multiple neurological systems.

Key Diagnostic Distinction

The presence or absence of sphincter dysfunction is critical for differential diagnosis:

• Isolated cerebellar disease (pure spinocerebellar ataxias) rarely causes significant sphincter dysfunction 1, 2
• MSA with cerebellar features (MSA-C) presents with the combination of cerebellar ataxia, pyramidal signs, and dysautonomia including urinary incontinence in the majority of cases 1
• MSA typically has onset between 55-65 years of age with mean disease duration of approximately 6 years 1

Urinary Dysfunction in Spinocerebellar Ataxias

While traditionally not considered a primary feature, lower urinary tract symptoms (LUTS) do occur in spinocerebellar ataxias more frequently than previously recognized:

• 15% of patients with genetically confirmed SCAs have LUTS 3
• When present, urinary frequency is the most common symptom (72.7% of those with LUTS), followed by voiding difficulty 3
• In SCA6 specifically, urinary symptoms occur in 56% of patients, with urinary frequency in 33% 4
• Storage and voiding symptoms are reported in 86.3% of SCA patients when systematically assessed with validated questionnaires, though often mild 5

Urodynamic Findings in SCAs

When urodynamic studies are performed in SCA patients with urinary complaints:

• Detrusor overactivity occurs in approximately 11-21% 3, 4
• Detrusor underactivity during voiding phase is common 5
• Post-void residual >100ml occurs in some patients 3
• Neurogenic bladder changes can be documented 3
• True urinary retention is rare 4

Clinical Implications and Red Flags

When to Suspect MSA Rather Than Pure SCA

The combination of cerebellar ataxia with significant urinary incontinence should raise immediate concern for MSA rather than isolated cerebellar disease 1. MSA is distinguished by:

• Abnormal cytoplasmic inclusions of alpha-synuclein in oligodendroglia 1
• Progressive autonomic dysfunction including urinary incontinence 1
• Often coexisting Parkinsonian features 1

Bowel Dysfunction

• Fecal incontinence is a "white flag" indicating severe neurological compromise when present with cauda equina syndrome 6
• In SCAs, bowel symptoms are less common (31.4%) and tend to be mild 5
• Significant bowel dysfunction with cerebellar ataxia suggests pathology beyond the cerebellum

Diagnostic Approach

Initial Imaging

• MRI of the head without IV contrast is the preferred initial imaging modality for evaluating cerebellar ataxia 6, 2
• MRI provides superior visualization of the posterior fossa and can detect morphologic changes and signal alterations in cerebellum and brainstem 6, 2
• Look for patterns suggesting MSA versus isolated cerebellar atrophy 1, 2

Laboratory Evaluation When Sphincter Dysfunction Present

Test for autoimmune and paraneoplastic causes when cerebellar ataxia occurs with autonomic dysfunction:

• GAD antibodies 1
• Glycine receptor antibodies (GlyR-Abs) 1
• CASPR2 antibodies 1
• Voltage-gated calcium channel antibodies (VGCC-Abs) 1
• Screen for underlying malignancy, particularly lung cancer in older patients 1

Management Considerations

Treatment of Urinary Symptoms

• 77.6% of SCA patients with urinary symptoms report impact on quality of life, yet 55.3% receive no pharmacological treatment 5
• These symptoms are frequently overlooked due to focus on primary neurological manifestations 5
• A multidisciplinary approach including urology consultation should be adopted 5

Immunotherapy-Responsive Conditions

When autoimmune etiology is identified:

• Patients with GlyR-Abs respond well to intravenous immunoglobulins and corticosteroids 1
• Early immunotherapy is critical to prevent permanent cerebellar damage in paraneoplastic syndromes 1

Clinical Pitfall

The most important pitfall is misdiagnosing MSA-C as a pure spinocerebellar ataxia when urinary dysfunction is present 3. A patient with progressive cerebellar ataxia without family history who develops significant urinary incontinence should be evaluated for MSA rather than assumed to have hereditary SCA 3.