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The "spray can" sign: validation of a clinical observation in chronic inflammatory demyelinating polyneuropathy
Sean J Pittock1, Dara Meldrum, Orla Hardiman
1Department of Neurology, Beaumont Hospital, Beaumont Road, Dublin 9, Ireland.
Background:
The presentation of chronic inflammatory neuropathies is variable. The decision regarding when to intervene with treatment is ideally determined by identifying early markers of loss of function.
Objective:
To test the hypothesis that an observation of functional impairment, defined by a patient with demyelinating neuropathy, can be used as a reproducible and reliable measure of improvement with intravenous immune globulin.
Design:
A 28-year-old woman presented with a chronic inflammatory demyelinating polyneuropathy. Her first complaint was the inability to use her deodorant spray because of hand weakness. A calibrated pincer gauge fixed on top of her usual spray can was used to objectively test finger flexion. Tip grip and lateral pinch were also measured. A calibrated dynamometer was used to measure grip strength.
Results:
Power and precision grip force were reproducible in normal control subjects by means of the spray can test. This test proved to be a reliable indicator of reduced muscle strength in the patient and improved after treatment with intravenous immune globulin.
Conclusions:
The spray can test objectively quantified the daily function, nominated by the patient, of operating an aerosol can. This measurement, drawn from a functional loss observed by the patient, proved to be a portable and reliable indicator of decline and recovery in chronic inflammatory demyelinating polyneuropathy.