A case of nocturnal polyuria in olivopontocerebellar atrophy

INTRODUCTION

Shy–Drager syndrome (SDS) and olivopontocerebellar atrophy (OPCA) are classified as multiple system atrophy associated with an autonomic disturbance. It has been reported that nocturnal polyuria exhibited by some SDS patients is related to a disturbance in the circadian rhythm of arginine vasopressin (AVP) secretion due to degeneration of suprachiasmatic nuclei.¹ The present study investigated the mechanism from the standpoint of biological rhythm by simultaneous measurement of diurnal variation of circadian parameters in an OPCA patient with marked nocturnal polyuria.

CASE REPORT

We describe a 54-year-old woman with a 7-year history of OPCA, and no remarkable family or previous history. Neurological symptoms included cerebellar ataxia, dysuria and orthostatic hypotention. The patient was virtually bedridden due to akinesia. Sleep apneas were not observed. Following urethral catheterization due to a dysuria, the patient was almost oliguric during the day. Since the patient had nocturnal polyuria, the daytime (06.00–18.00 h) and night-time (18.00–06.00 h) urinary volume and urinary specific gravity were measured for 5 days. She had not suffered from polydipsia. To investigate the etiology of the nocturnal polyuria, plasma concentrations of AVP, cortisol, and atrial natriuretic peptide (ANP) were determined every 6 h, rectal temperature, heart rate, and actigraphy were measured simultaneously at 1-min intervals using a Mini-Logger SERIES 2000. Blood pressure was measured non-invasively every 15 min using an ambulatory blood pressure monitoring device (TM-2425, A&D). Meals were provided at 07.30, 12.00 and 18.00 h. Levodopa and triphexyphenidil were administrated 300 mg/day and 6 mg/day. Fluid intake was not measured, and the patient could drink at will.

RESULTS

(1) The mean daytime urinary volume and urinary specific gravity over 5 days were 299 mL and 1.019, and the corresponding values for night-time were 928 mL and 1.009, respectively. A low specific gravity consistent with polyuria was observed at night (Fig. 1).

(2) Rectal temperature and heart rate exhibited a circadian rhythm, and sleep–wake regulation was maintained as evidenced by motor activity which was evaluated using an actigraphy.

(3) There were marked short-term variations in blood pressure both daytime and night-time, and diminished nocturnal blood pressure decline (Fig. 2).

(4) The circadian rhythm of plasma cortisol was maintained but the constant circadian rhythm, such as that reported by George et al.² in healthy people, was not obtained for the plasma concentration of AVP (Fig. 3).

(5) A marked elevation in ANP secretion was observed during the night (Fig. 3).

DISCUSSION

Lackwood³ has shown that polyuria in SDS patients is due to a partial defect of antidiuretic hormone secretion. Ozawa et al.,¹ on the other hand, argued that a disturbance in the circadian rhythm of AVP secretion was due to degeneration of suprachiasmatic nuclei. Although the circadian rhythm of rectal temperature, heart rate, and cortisol secretion were maintained in this case, a constant circadian rhythm of AVP secretion was not observed. It is considered that a selective disturbance of AVP-secreting neurons in the hypothalamus is involved. According to the previous paper,⁴ control subjects had a nocturnal increase in the plasma concentration of ANP. The mechanism of increase in the plasma concentration of ANP during the night is likely to be due to the increase in the right atrial pressure that occurs during recumbency. Although Kaufmann et al.⁵ reported low plasma ANP concentration at night in multiple system atrophy, this case showed a marked elevation of ANP secretion during the night. The release of ANP during sleep increases in patients with obstructive sleep apnea.⁶ Although some patients with OPCA also had sleep apnea syndrome,⁷ sleep apnea was not observed in this case. It is suggested that a marked ANP secretion during the night has probably no association with sleep apnea in this case, but is related to an elevation in the blood pressure during the night.

The possible mechanisms of the nocturnal polyuria observed in this case are speculated to be due to a disturbance in the circadian rhythm for AVP secretion and the marked ANP secretion during the night.