How Can Stiff-Person Syndrome Be Mistaken for Other Conditions?

What you need to know

• Stiff-person syndrome (SPS) is a rare neurological disorder that causes muscle stiffness and painful spasms
• SPS can be mistaken for psychiatric conditions or other neurological disorders, delaying proper diagnosis and treatment
• Specific antibody tests and careful evaluation of symptoms are key to diagnosing SPS accurately

Understanding Stiff-Person Syndrome

Stiff-person syndrome (SPS) is an uncommon neurological disorder that can significantly impact a person’s quality of life. This condition causes progressive muscle stiffness and painful spasms, often leading to difficulty walking and fear of falling. Despite its severe symptoms, SPS is frequently misdiagnosed, which can delay proper treatment. This article explores a case that highlights the challenges in diagnosing SPS and provides insights to help patients and families recognize its key features.

A Puzzling Case

The case study describes a 52-year-old woman who experienced episodes of back and thigh stiffening every few months for five years. Her symptoms worsened over time, causing multiple falls and making it difficult for her to walk without a cane. Eventually, she became housebound due to fear of falling.

When examined, the patient showed sudden muscle spasms triggered by touch, noise, and light. She was taking antidepressant medication and had a fever, excessive sweating, and high levels of a muscle enzyme called creatine kinase (CK) in her blood. Initially, doctors suspected a condition called neuroleptic malignant syndrome (NMS), which can be a side effect of certain medications.

The Path to Diagnosis

Further testing revealed crucial information:

1. Very high levels of antibodies against glutamic acid decarboxylase (GAD) in the blood
2. Presence of oligoclonal bands in the cerebrospinal fluid (the liquid surrounding the brain and spinal cord)

These findings, combined with the patient’s symptoms, led to the correct diagnosis of stiff-person syndrome.

Key Features of Stiff-Person Syndrome

Symptoms

SPS typically begins in adulthood and is characterized by:

• Progressive muscle stiffness, especially in the trunk and limbs
• Sudden, often painful muscle spasms
• Difficulty walking or moving normally
• Exaggerated curvature of the lower back (lumbar lordosis)
• Anxiety and fear of falling or open spaces

Triggers

Muscle spasms in SPS can be set off by various stimuli, including:

• Unexpected touch or physical contact
• Loud noises
• Bright lights
• Emotional stress

Autoimmune Nature

SPS is believed to be an autoimmune disorder, meaning the body’s immune system mistakenly attacks its own tissues. In SPS, the immune system targets proteins involved in regulating muscle movement, leading to the characteristic stiffness and spasms.

Diagnostic Challenges

Mimicking Other Conditions

The case highlights how SPS can be mistaken for other disorders, particularly when patients are taking psychiatric medications. Some conditions that may be confused with SPS include:

1. Neuroleptic malignant syndrome (NMS)
2. Serotonin syndrome
3. Anxiety disorders or phobias

The Role of Creatine Kinase

Creatine kinase (CK) is an enzyme released when muscle tissue is damaged. In this case, the patient’s CK levels were very high (16,200 U/L), which is more typical of NMS or serotonin syndrome than SPS. However, the authors note that severe muscle spasms in SPS can sometimes cause muscle breakdown, leading to elevated CK levels.

This case demonstrates that while CK levels can be a helpful diagnostic tool, they should not be the sole factor in determining a diagnosis. The characteristic muscle stiffness and spasms of SPS, along with specific antibody tests, are crucial for accurate diagnosis.

Diagnostic Tests for Stiff-Person Syndrome

To diagnose SPS, doctors typically use a combination of:

1. Clinical evaluation of symptoms and physical examination
2. Blood tests for anti-GAD antibodies (which are often elevated in SPS)
3. Analysis of cerebrospinal fluid for signs of inflammation or immune system activity
4. Electromyography (EMG) to measure muscle activity
5. Imaging studies to rule out other conditions

Treatment Approaches

Once correctly diagnosed, the patient in this case received treatments targeting the autoimmune nature of SPS:

1. Plasma exchange: A procedure that removes and replaces blood plasma to reduce harmful antibodies
2. Intravenous immunoglobulin: An infusion of antibodies that can help modulate the immune system
3. Oral diazepam: A medication that helps reduce muscle spasms and anxiety

With appropriate treatment, the patient’s condition improved significantly, and she regained the ability to walk without difficulty or anxiety.

Living with Stiff-Person Syndrome

While SPS is a chronic condition, proper management can greatly improve quality of life. Patients with SPS may benefit from:

• Medications to reduce muscle stiffness and spasms
• Immunotherapy to address the autoimmune component
• Physical therapy to maintain mobility and strength
• Occupational therapy to adapt daily activities
• Psychological support to manage anxiety and stress
• Regular medical follow-ups to adjust treatment as needed

Conclusions

• Stiff-person syndrome is a rare but serious neurological disorder that can significantly impact mobility and quality of life.
• Accurate diagnosis of SPS can be challenging, as its symptoms may mimic other neurological or psychiatric conditions.
• A combination of clinical evaluation, specific antibody tests, and careful consideration of symptoms is crucial for proper diagnosis and treatment of SPS.
• With appropriate management, many people with SPS can experience significant improvement in their symptoms and daily functioning.