What are the symptoms and treatment options for Stiff Person Syndrome?

Symptoms of Stiff Person Syndrome (SPS)

Stiff Person Syndrome is characterized by progressive muscle rigidity and painful spasms primarily affecting the axial and limb muscles, with associated continuous motor unit activity on electromyography and often the presence of glutamic acid decarboxylase (GAD) antibodies.

Core Clinical Features

Primary Symptoms

• Progressive muscle rigidity and stiffness

  • Predominantly affects axial muscles (trunk, abdomen, back)
  • Often involves proximal limb muscles
  • Usually symmetric but can be asymmetric in variants 1
  • Leads to characteristic stiff, wooden posture

• Painful muscle spasms

  • Superimposed on baseline rigidity
  • Can be severe and debilitating
  • Triggered by various stimuli:
    • Tactile stimuli/touch
    • Sudden noises or emotional stress
    • Passive stretching of muscles
    • Voluntary movement 2

• Continuous motor unit activity

  • Detectable on electromyography (EMG)
  • Persists even at rest
  • Characteristic diagnostic finding 3

Variant Presentations

SPS can present in different clinical forms:

1. Classic SPS

   • Widespread axial and limb rigidity with spasms

2. Focal/Segmental SPS

   • Symptoms confined to specific body regions
   • May affect just one limb or group of muscles 4

3. Jerking SPS

   • Features prominent myoclonic jerks
   • More sudden movements compared to classic form 1

4. Progressive Encephalomyelitis with Rigidity and Myoclonus

   • More severe variant with brainstem and spinal cord involvement
   • Often rapid progression 1

Associated Features and Complications

• Exaggerated startle response

  • Heightened sensitivity to unexpected stimuli
  • Can trigger severe spasms

• Gait abnormalities

  • Slow, stiff walking pattern
  • Increased risk of falls

• Postural deformities

  • Lumbar hyperlordosis
  • Thoracic kyphosis
  • Joint contractures in advanced cases

• Autonomic disturbances

  • Can include sweating, tachycardia, pupillary abnormalities
  • May occur during spasms

• Psychiatric symptoms

  • Anxiety and depression common
  • Often related to chronic pain and disability 3

Diagnostic Biomarkers

• Anti-GAD65 antibodies

  • Present in 60-80% of SPS cases
  • Higher titers than in other GAD-associated disorders 1

• Other antibodies

  • Anti-amphiphysin (often in paraneoplastic cases)
  • Anti-GABA(A) receptor-associated protein
  • Anti-glycine-α1 receptor 1

Disease Associations

• Autoimmune disorders

  • Type 1 diabetes mellitus
  • Thyroiditis
  • Vitiligo
  • Pernicious anemia 2

• Paraneoplastic associations

  • Breast cancer (most common)
  • Small cell lung cancer
  • Thymoma
  • Hodgkin lymphoma 4

Clinical Course and Prognosis

• Progressive nature

  • Symptoms typically worsen over time without treatment
  • Spontaneous remissions are rare 1

• Disability impact

  • Can lead to significant functional impairment
  • Affects mobility and activities of daily living
  • May eventually require assistive devices or wheelchair 3

• Quality of life

  • Chronic pain and spasms significantly reduce quality of life
  • Psychological impact often substantial
  • Social isolation common due to disability 4

Relieving Factors

• Sleep

  • Symptoms typically disappear during sleep
  • Return upon awakening

• Sedation

  • General anesthesia
  • Benzodiazepines and other GABAergic medications 2

Treatment Approaches

While not part of the symptoms, it's worth noting that treatment typically involves:

1. GABAergic medications

   • Benzodiazepines (diazepam, clonazepam)
   • Baclofen (oral or intrathecal)
   • Anticonvulsants (levetiracetam, pregabalin) 5

2. Immunotherapy

   • Intravenous immunoglobulin (IVIG)
   • Plasmapheresis
   • Rituximab
   • Corticosteroids 5

Early diagnosis and treatment are essential to prevent progression and improve quality of life in patients with this challenging neurological disorder.