The exercise test in Andersen syndrome.
BACKGROUND
Andersen syndrome is a rare form of periodic paralysis (PP) associated with dysmorphic features and potentially fatal cardiac dysrhythmias. To date, no electrodiagnostic abnormalities have been reported that can be used to confirm the presence of PP in this condition.


OBJECTIVE
To determine if the exercise test could be used to confirm the diagnosis of PP in Andersen syndrome. To evaluate the exercise test as a means to assess neuromuscular status during treatment.


METHODS
We performed the exercise test on 2 patients with Andersen syndrome. In 1 patient, we used a modified version of the test to document responsiveness to treatment with tocainide.


RESULTS
Studies in both patients demonstrated a progressive decline in the compound muscle action potential amplitude after exercise that was characteristic of the phenomenon seen in other forms of PP. In 1 patient, improvement in interattack strength and a reduction in the number of attacks of weakness correlated with improvement in the test results.


CONCLUSIONS
Our cases demonstrate that the exercise test can confirm the diagnosis of PP in Andersen syndrome. A modified version of exercise testing may also be considered as an objective method for documenting treatment responses in PP.
Katz
J S
JS
Department of Veterans Affairs, Department of Neurology, Stanford University School of Medicine, Palo Alto, Calif 94304, USA.
Wolfe
G I
GI
Iannaccone
S
S
Bryan
W W
WW
Barohn
R J
RJ
D000015:Abnormalities, Multiple; D000200:Action Potentials; D000293:Adolescent; D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D005080:Exercise Test; D005147:Facial Bones / Q000002:abnormalities; D005260:Female; D006801:Humans; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000188:drug therapy / Q000209:etiology; D008297:Male; D018908:Muscle Weakness; D010245:Paralyses, Familial Periodic / Q000175:diagnosis*; D016677:Tocainide / Q000627:therapeutic use
D000889:Anti-Arrhythmia Agents; D016677:Tocainide