Stiff Person Syndrome Workup

Updated: Sep 06, 2023
  • Author: Nancy Theresa Rodgers-Neame, MD; Chief Editor: Nicholas Lorenzo, MD, CPE, MHCM, FAAPL  more...
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Laboratory Studies

Obtain the following laboratory tests and interpret the results as outlined in Pathophysiology:

  • Hemoglobin A1C: This is obtained because of association with diabetes mellitus.

  • Complete blood count: An association with pernicious anemia has been reported.

  • Comprehensive metabolic profile

  • Thyroid-stimulating hormone: Thyroiditis is sometimes associated.

Special tests include the following:

  • Anti-GAD antibodies

  • Anti–pancreatic islet cell antibodies

  • Anti-amphiphysin antibodies


Imaging Studies

MRI or CT scanning of the brain is only indicated if cortical or corticospinal tract signs are present on examination, for example, frontal lobe signs, increased reflexes, clonus, or abnormal plantar reflexes.

Chest CT may also be indicated. Several individual case studies have reported thymoma in stiff person syndrome.


Other Tests

Other tests that may prove useful include the following:

  • Electromyography (EMG): Characteristic continuous motor unit activity with normal morphology is especially prominent in the paraspinal muscles. Myotonic potentials are absent. Activity resolves with sleep and abates with benzodiazepines (diazepam). Simultaneous continuous motor activity is noted in opposing muscles.

  • Electroencephalography: EEG is indicated when episodic or paroxysmal stiffness occurs or signs of cortical abnormalities are present on examination. Rare cases of stiff person syndrome with associated refractory partial epilepsy have been reported. [15]



Lumbar puncture and associated CSF studies should be obtained in patients with a presentation that is consistent with stiff person syndrome to rule out other etiologies. Oligoclonal bands can be observed in approximately two thirds of patients with antibody-positive stiff person syndrome. [20] In addition, lumbar puncture can add needed information if the patient's presentation is unusual or complex.