Acta Neurol Belg DOI 10.1007/s13760-014-0381-0

LETTER TO THE EDITOR

Isolated unilateral leg weakness as the presenting symptom of primary aldosteronism: a case report Jin-Sung Park • Jun Nyung Lee • Jin-Hong Shin

Received: 27 August 2014 / Accepted: 14 October 2014 Ó Belgian Neurological Society 2014

Keywords Primary aldosteronism  Hypokalemic paralysis  Physical stress  Leg weakness  Activity-dependent conduction block

Introduction Primary aldosteronism is an uncommon cause of secondary arterial hypertension occurring in approximately 2 % of the unselected patients. It is due to an aldosterone-producing adenoma in adrenal gland, which sometimes leads to profound hypokalemia. The patients usually present with uncontrolled hypertension, polyuria, general weakness, cramps, headache and rhabdomyolysis. In severe cases, hypokalemia may cause muscle weakness in the extremities [1]. We report a case of an isolated unilateral leg weakness in a patient with adrenal adenoma, whose weakness improved by potassium replacement and later eliminated by the removal of the underlying adenoma.

J.-S. Park Department of Neurology, School of Medicine, Kyungpook National University Hospital, Daegu, Korea e-mail: [email protected] J. N. Lee Department of Urology, School of Medicine, Kyungpook National University Hospital, Daegu, Korea J.-H. Shin (&) Department of Neurology, Pusan National University Yangsan Hospital, Yangsan, Korea e-mail: [email protected]

Case A 44-year-old male presented with left leg weakness that caused difficulty in walking for half a day. He claimed that he had been suffering from leg pain for a week after kicked in his shin, which resulted in the weakness. He had been on anti-hypertensive medication for 5 years. Initial blood pressure was 170/100 mmHg with heart rate of 100 per min. With his alert mentality, neurological examination revealed no abnormality but the weakness in his left leg. The weakness corresponded to grade IV in leg flexion, grade III in ankle dorsiflexion, measured by medical research council system. His deep tendon reflexes were hypoactive while neither sensory symptoms nor pathologic reflexes are noted. The laboratory findings revealed more clues: mild elevation of creatinine phosphokinase (CPK) to 552 IU/L with markedly reduced serum potassium of 1.7 mmol/L. Other laboratory findings including thyroid function, ionized electrolytes and autoimmune indices were all within normal limits. Nerve conduction study demonstrated mildly reduced amplitudes of compound motor action potentials on the left peroneal nerve compared to the right side. In search of the cause of profound hypokalemia, we found an increase in his renin and aldosterone level that was elevated to 35 ng/dL and 0.03 ng/ml/h, respectively, in supine position, giving a calculation of aldosterone-torenin ratio (ARR) of 1,116.7. The renin and aldosterone level was unsuppressed by the saline load, to the level of 51.2 ng/dL and 0.26 ng/ml/h, respectively, with ARR of 196.9. The abdominal computed tomography demonstrated a mass ranging 2.6 cm in diameter situated near his left adrenal gland (Fig. 1a) to give final diagnosis of primary aldosteronism due to adrenal adenoma. Two days of

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Fig. 1 The axial computed tomography shows a left adrenal mass with an attenuation value of -2 HU in keeping with a benign lipidrich adrenal adenoma (a). The gross finding of the tumor shows round shaped and yellowish adrenal adenoma (b). The initial compound

motor action potentials (CMAP) of the symptomatic left peroneal nerve is reduced (c) compared to the right side and after potassium replacement, CMAP was reversibly increased (d) without his left leg weakness

continuous intravenous potassium administration (120–200 mEq/day) along with 100 mg of spironolactone recovered his potassium level up to 2.8 mEq/L and improved his left leg weakness. After 2 weeks, laparoscopic adrenalectomy was performed and gross pathologic examination confirmed adrenal cortical adenoma (Fig. 1b). After the surgery, his follow-up NCS demonstrated a reversibly increased CMAP amplitude in the left peroneal nerve (Fig. 1c, d) and he turned free of focal or generalized weakness.

acquired, including thyroid disease, renal disorders, gastrointestinal potassium loss and endocrinopathies. Primary aldosteronism is a disorder in which aldosterone is inappropriately produced independent of the renin– angiotensin system. Aldosterone by adrenal adenoma is not physiologically suppressed by sodium loading. Overproduction of aldosterone increases Na? reabsorption with excessive K? secretion in distal renal tubule, and eventually leads to hypokalemia. Decreased serum K? induces a reversible change in the membrane excitability that neurological symptoms may appear when serum K? drops below 2.5 mEq/L [2]. Hypokalemic paralysis most typically demonstrates a flaccid, hyporeflexic and symmetric proximal weakness, more often in the upper extremities [2]. Interestingly, a few reports describe asymmetric or unilateral limb weakness during hypokalemic paralysis [3, 4]. One case report demonstrated unilateral weakness without imaging

Discussion Potassium plays a crucial role in the maintenance of the membrane potentials and hypokalemic conditions are known to aggravate hyperpolarization of the cell membrane. The cause of hypokalemia can be genetic or

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evidence of the brain magnetic resonance imaging and the authors suggested a possibility of subclinical corticospinal pathway damage, aggravated by hypokalemia [3]. Recently, another case report illustrated a focal weakness in the hand that was always provoked after playing piano. It was later found to be due to secondary hypokalemia by primary aldosteronism and the excision of the adrenal mass cured her symptom [4]. These reports with focal weakness with systemic hypokalemia are all related to hyperaldosteronism, distinct from the genetic condition of hypokalemic periodic paralysis. Krishnan et al. [5] suggested an activity-dependent conduction block as pathomechanism of hypokalemic weakness by hyperaldosteronism, though they could not completely exclude decreased excitability by sarcolemmal hyperpolarization. Our case, the first report of one-leg weakness by primary aldosteronism to our best knowledge, may also be explained by activity-dependent phenomenon, as the preceding trauma and pain on his left leg is supposed to accompany unnatural strain on the leg muscles. Evidenced with the lower CMAP amplitude in the peroneal nerve of the affected side which recovered after the treatment, our case reinforces that the hypokalemic weakness can occur in

any limb and it is possibly related to physical activity in the setting of hypokalemia. Acknowledgments This study was supported by Clinical Research Fund 2013, Pusan National University Yangsan Hospital. Conflict of interest

None.

References 1. Hiraga A, Kamitsukasa K, Kojima K, Kuwabara S (2012) Clinical features and recovery patterns of acquired non-thyrotoxic hypokalemic periodic paralysis. J Neurol Sci 313:42–45 2. Riggs JE (2002) Neurologic manifestations of electrolyte disturbances. Neurol Clin 20:227–239 3. Lu YT, Lan MY, Liu JS, Chen WH (2011) An unusual presentation of hypokalemic paralysis with evolving pure motor hemiparesis. J Clin Neurosci 18:716–719 4. Chui C, Chen WH, Yin HL (2014) Periodic drop thumb, hypokalemia and adrenal adenoma. Med Princ Pract 23:80–82 5. Krishnan AV, Colebatch JG, Kiernan MC (2005) Hypokalemic weakness in hyperaldosteronism: activity-dependent conduction block. Neurology 65:1309–1312

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Isolated unilateral leg weakness as the presenting symptom of primary aldosteronism: a case report.

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