Neurology Diagnoses Stiff Person Syndrome
Stiff Person Syndrome (SPS) should be diagnosed by a neurologist, specifically one with expertise in autoimmune neurology or movement disorders. 1, 2
Primary Diagnostic Specialty
Neurology is the primary specialty responsible for diagnosing SPS, as this is a rare autoimmune neurological disorder characterized by progressive muscle rigidity, painful spasms, and continuous motor unit activity. 3, 4, 5
Patients with suspected SPS should be referred to a neurologist for initial evaluation, with the referral urgency depending on symptom severity (typically within 2-4 weeks for stable cases). 1
For complex or diagnostically uncertain cases, referral to an autoimmune neurologist is strongly recommended, as SPS diagnosis can be challenging and misdiagnosis is threefold more common than confirmed SPS. 2
Why Neurology Specifically
The diagnosis requires specialized neurological assessment including:
Detailed neurological examination to identify characteristic findings: hypertonia (60% of cases), hyperreflexia (71%), lumbar hyperlordosis (67%), and exclusion of functional neurologic signs. 2
Electromyographic (EMG) evaluation showing continuous motor unit activity in agonist and antagonist muscles, which is essential for diagnosis, particularly in seronegative cases. 6, 2
Specialized antibody testing interpretation: GAD65-IgG (>20.0 nmol/L), glycine-receptor-IgG, or amphiphysin-IgG, with understanding that GAD65 antibody patterns differ between SPS and diabetes. 1, 2
Assessment of response to benzodiazepines (51% show moderate improvement) and immunotherapy (45% improve), which helps confirm diagnosis. 2
Common Diagnostic Pitfalls
SPS is frequently misdiagnosed as psychiatric illness (as occurred in one case with an 11-year delay), pain syndromes, or functional neurologic disorder (65% of misdiagnosed cases). 6, 2
A thorough neurological examination is essential to exclude peripheral neuropathy, radiculopathy, or other movement disorders that can mimic SPS. 7
The general neurologist may only see one or two cases during their career, making it underdiagnosed and requiring high clinical suspicion. 4
Multidisciplinary Involvement
While neurology is primary, other specialties may be involved:
Endocrinology consultation may be needed given the association with diabetes and other autoimmune diseases, though this is for co-management rather than primary diagnosis. 7, 1
Oncology referral is indicated when paraneoplastic SPS is suspected (associated with anti-amphiphysin antibodies and breast cancer). 3, 5