Peripheral neurological changes in chronic obstructive pulmonary diseases: Clinical and electrophysiological studies

ABSTRACT

Twenty five patients with COPD with mean age of 55.4 +/- 8.7 years have been investigated with pulmonary function tests [PFT], arterial blood gases [ABG], serum electrolytes [Na, K, Ca++], neurological examination and electrophysiological studies. Symptoms of neuropathy were present in 36% of the patients, while clinical signs were found only in 20%. Orthodromic distal sensory latency was prolonged in 44% of cases with lowering of amplitude of the evoked sensory action potential. Abnormalities of the sensory nerve conduction were the most common and affecting mainly the sural nerve. Motor conduction velocity was abnormal in 16% of cases. Sixteen percent of COPD patients exhibited impairment of both sensory and motor functions. Abnormal electromyographic [EMG] findings were detected in 11 cases [44%]. The EMG changes were abnormal resting potential, incomplete interference pattern and polyphase motor unit. These denoted the existence of both myelinopathic and axonopathic changes. Comparative study of COPD patients with neurological impairment [group I] versus COPD patients without such defect [group II] regarding PFT, ABG and serum electrolytes revealed insignificant difference in PFT and serum electrolytes between both groups. However, patients of group I were more hypoxemic and hypercapnic than group II patients and the difference in PaO2 and PaCO2 were statistically significant [P <0.01]. It was concluded that peripheral neuropathy is not uncommon finding in COPD and it seems possible that severe derangement in ABG in form of hypoxemia and hypercapnia are responsible for the encountered neurological abnormalities