Correction

Abstract

Abstract-The authors performed nerve conduction studies in nine PARK2 and eight idiopathic Parkinson disease patients and found a significant reduction of sural sensory nerve action potential (SNAP) amplitude in eight PARK2 patients who mostly remained asymptomatic. These data suggest that sensory axonal neuropathy may be a common clinical feature of PARK2 and a reduced amplitude of sural SNAP could be a diagnostic indicator of PARK2. Numbness, tingling, burning, and pain are common sensory symptoms of Parkinson disease (PD). 1 Several lines of evidence (e.g., the lack of objective sensory loss, the normal nerve conduction study [NCS], 1 the high occurrence on levodopa-off period, and the drastic improvement of pallidal deep brain stimulation) suggest that these sensory symptoms are not of peripheral but of CNS origin. However, 11 of 29 patients with juvenile parkinsonism of unknown etiology showed abnormal NCS in peroneal motor or sural sensory nerves.2 We investigated two autosomal recessive juvenile parkinsonism (PARK2) patients complaining of a tingling sensation with objective sensory loss in the foot (Patients 1, 2 in the table). Based on reduced sural sensory nerve action potential (SNAP) amplitude in these patients, we hypothesized that a mutation of the PARK2 causative gene, Parkin, 3 results in sensory axonal neuropathy. We investigate this hypothesis by examining NCSs in a series of PARK2 and idiopathic PD patients, together with the expression analysis of the Parkin gene in the peripheral nervous system.Methods. We performed this study in patients under the age of 60 years, because sural SNAP amplitude reduces with aging, and is sometimes absent even in normal subjects over the age of 70 years.4,5 Diagnosis of PARK2 was confirmed by DNA analysis using exonic PCR amplification of the Parkin gene as described previously.3 All PARK2 or idiopathic PD patients were interviewed to determine whether they were experiencing sensory symptoms. Those patients with other causes of neuropathy (e.g., medications including amantadine, exposure to toxins, diabetes mellitus, uremia, hypothyroidism, pernicious anemia, vitamin B6 deficiency, alcohol abuse, syphilis, gammopathy, malignancy, collagen vascular disease) as determined by laboratory testing or medical consultation were excluded from this study. Patients with obesity or leg swelling were also excluded. Seventeen patients with PARK2 or idiopathic PD were enrolled in this study. Two patients, who were clinically diagnosed with idiopathic PD, turned out to have sporadic PARK2 by DNA analysis.NCS was performed on the median motor and sensory, the ulnar motor and sensory, the tibial motor, the peroneal motor, and the sural sensory nerves using standard methods described previously.4,5 For sural NCS, signal averaging of 20 to 50 responses was used. Peak-to-peak amplitude was used for the amplitude measurement and nerve conduction velocity (NCV) was calculated using the onset latency.4,5 Age-and sex-matched normal control subjects (20 men, 50.2 Ϯ 5.3 years old; 20 wo...