Recurrent hyponatremia as the presenting feature of a pituitary abscess: A case report.

A pituitary abscess is a rare but serious intrasellar infection. It was first described by Simonds in 1914 and since then, only about 100 cases have been reported in the English speaking literature. Most patients develop symptoms and signs of meningitis or pituitary neoplasm. Indeed, the predominant clinical features of pituitary abscesses resemble those of pituitary adenomas and they are usually accompanied by either endocrinological disturbances or symptoms related to a mass effect. Syndrome of inadequate antidiuretic hormone secretion (SIADH) is not an uncommon complaint in association with neurological disorders, although very few cases of SIADH have been reported in association with a pituitary mass. Here, we describe the unusual case of a patient with a pituitary abscess that manifested severe hyponatremia, with no signs or symptoms of local or systemic infection. Case report: A 53 year-old man was admitted to our hospital complaining of extreme weakness, right frontal headache and photophobia. He also complained of having suffered recurrent headaches, anorexia, asthenia, bradypsychia and erectile dysfunction over the previous months. For the past 5 years he had been following treatment with glibenclamide and statins for type 2 diabetes and hypercholesterolemia, respectively, and he had achieved good glycaemic control. When examined clinically he was not thirsty and showed no signs of oedema or dehydration. He presented signs of hypopituitarism, with dry skin, scant axillary and pubic hair, and small and soft testes. His temperature was 36.1 1C and he showed no signs or symptoms of local or systemic infection. However, bilateral temporal quadrantanopsia was found on ophthalmologic examination and in biochemical assays he had a serum sodium concentration of 128mEq/L and urinary sodium of 45mEq/L. Endocrine tests at admission revealed the following levels in the serum: cortisol, 1.6 mg/dL; prolactin (PRL), 0.6 ng/dL; follitropin (FSH), 0.16mU/mL; thyrotropin (TSH), 0.45 uU/mL; and free thyroxine (FT4), 0.40 ng/mL. Magnetic resonance imaging (MRI) of the pituitary identified a 3 cm intrasellar mass that extended to both cavernous sinuses and to the optic chiasm, and it was of low-intensity in T1 weighted sequences and high-intensity in T2 weighting (Figure 1A). As a result, a pituitary adenoma was diagnosed. Mild hyponatremia persisted after replacement therapy with hydrocortisone and levothyroxine, and the patients’ fluid intake needed to be restricted until he underwent transsphenoidal surgery (Figure 1). Histopathological examination of the resected tissue revealed a necrotic material from which aerobic and anaerobic cultures were negative. After surgery, the patient recovered from the ophtalmoplegia but his hypopituitarism persisted and as such, replacement therapy was continued. Two months later, the patient again complained of severe headache, nausea and decreased visual acuity. A cranial MRI showed a 2.5 cm heterogeneous intrasellar mass that was hypointense on T1 and hyperintense on T2 weighting (Figure 1B). Initial laboratory studies while on treatment with 60mg/day hydrocortisone and 100 mg/day thyroxine revealed serum sodium concentrations of 123mEq/L, glucose concentrations of 151mg/dL, potassium concentrations of 4.2mEq/L, and a plasma osmolality of 265mOsm/Kg. Urine sodium excretion was 80mEq/L and his urine osmolality was 310mOsm/kg. Inappropriate antidiuresis secondary to pituitary lesion was diagnosed and daily fluid intake was restricted to 1500ml. The patients’ serum sodium concentrations gradually normalized within 3 days and with restricted fluid intake they remained stable thereafter. He then underwent a second transsphenoidal intervention to remove the pituitary mass and the pathological diagnosis was of a non-specific inflammatory reaction and necrotic material. Aerobic and anaerobic cultures were again negative. A diagnosis of recurrent pituitary abscess was made and the patient was treated intravenously with ceftriaxone and metronidazol. After surgery, the patient sodium balance normalized and he did not need any further restriction of fluids. After a followup of two years, the patient continues with persistent hypopituitarism that is controlled by replacement therapy and his water balance is normal. No pituitary lesions having been observed subsequently on MRI (Figure 1C). ARTICLE IN PRESS