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The "Spray Can" Sign
Validation of a Clinical Observation in Chronic Inflammatory Demyelinating Polyneuropathy
Sean J. Pittock, MD, MRCPI;
Dara Meldrum, MSc;
Orla Hardiman, MD, FRCPI
Arch Neurol. 2002;59:1637-1640.
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.
From the Departments of Neurology (Drs Pittock and Hardiman) and Physiotherapy
(Ms Meldrum), Beaumont Hospital, Dublin, Ireland. Dr Pittock is now with the
Department of Neurology, Mayo Clinic, Rochester, Minn. Ms Meldrum is now with
the Department of Physiotherapy, Royal College of Surgeons Ireland, Dublin.
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