Tohoku J. Exp. Med., 2018 September, 246(1)

Abnormal Osmolality Gap Exists in Distal Symmetric Polyneuropathy

TETSUYA AKAISHI,1,2 TOSHIYUKI TAKAHASHI,1,3 ICHIRO NAKASHIMA4 and MASASHI AOKI1

1Department of Neurology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan
2Department of Education and Support for Community Medicine, Tohoku University Hospital, Sendai, Miyagi, Japan
3Department of Neurology, Yonezawa National Hospital, Yonezawa, Yamagata, Japan
4Department of Neurology, Tohoku Medical and Pharmaceutical University, Sendai, Miyagi, Japan

Distal symmetric polyneuropathy, represented by chronic inflammatory demyelinating polyneuropathy, is a popular neurological condition. Some cases are known to be associated with genetic mutations or serum auto-antibodies, but the exact mechanisms in most cases are unknown. Recently, osmotic factors have been suggested to trigger some neurological disorders, such as neuromyelitis optica. The aim of the present study was to assess the possible association of osmotic factors in the pathogenesis of distal polyneuropathy. We prospectively measured the serum levels of osmolality, electrolytes, total protein, albumin, blood urea nitrogen, glucose, and osmolality gap in the patients with acute distal polyneuropathy before treatments (n = 12) and those with other comprehensive neurological disorders such as multiple sclerosis and neurodegenerative diseases (n = 176). Then, we compared each osmotic fraction between the two groups. As a result, all of the 12 patients with acute distal polyneuropathy, including 4 patients with chronic inflammatory demyelinating polyneuropathy, showed abnormally high or low values of osmolality gap, compared to the others (p < 0.0001, F-test). In the patients with other diseases, there were 2 patients with abnormally high osmolality gap values, which were attributable to their hyperlipidemia or high titer of serum autoantibody unrelated to polyneuropathy. In conclusion, serum osmolality gap would be elevated or decreased in the acute phase of distal symmetric polyneuropathy. Osmotic imbalance between the serum and nerve cells, based on abnormal excess or deficit of some unidentified serum osmolytes, may be one of the mechanisms in symmetric polyneuropathy with unknown causes.

Key words —— CIDP; distal symmetric polyneuropathy; osmolality gap; osmotic imbalance; osmotic pressure

===============================

Tohoku J. Exp. Med., 2018, 246, 59-64

Correspondence: Tetsuya Akaishi, Department of Neurology, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8574, Japan.

e-mail: t-akaishi@med.tohoku.ac.jp