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Alicia R Jones, Alan McNeil, Christopher Yates, Bala Krishnamurthy and Peter S Hamblin

Summary

A variety of neoplastic, inflammatory and congenital conditions can cause pituitary stalk thickening. Differentiating between these causes is important as targeted treatment may be offered. Diagnostic work-up consists of a thorough history, examination, biochemical analysis and imaging. We present the case of a 33-year-old male who presented with diabetes insipidus and had pituitary stalk thickening on magnetic resonance imaging. Further investigations revealed an elevated CSF βhCG, which raised the possibility of an intracranial germ cell tumor. However, when repeated on four different assays, the βhCG levels were discordant. On serial imaging, the pituitary stalk thickening reduced slightly, which would be unexpected for a germ cell tumor. This case raises the difficulties interpreting CSF βhCG, as not all immunoassays for βhCG have been validated for use in CSF. The Roche Diagnostics Elecsys and Siemens Centaur assays have been validated for CSF βhCG, and so we advocate using one of these methods. If unavailable or serum/CSF results are ambiguous, serial MRI is appropriate, with pituitary stalk biopsy considered if the stalk measures >6.5 mm or other imaging abnormalities are present.

Learning points:

  • Most adult patients with central diabetes insipidus have imaging abnormalities on a pituitary MRI. The most common abnormalities are loss of the posterior pituitary bright spot and pituitary stalk thickening, both of which are non-specific.

  • Causes of pituitary stalk thickening include neoplastic, inflammatory, infective and congenital lesions.

  • Investigation of pituitary stalk thickening should encompass the many possible causes and include biochemical analyses as well as imaging of the chest, abdomen and pelvis. Further investigations should be guided by the clinical context, but may include testicular ultrasound, CSF analysis and pituitary stalk biopsy.

  • Germ cell tumors involving the pituitary stalk may be suspected on clinical grounds, but in the absence of a tissue diagnosis (biopsy) confirmation may be difficult and relies on biochemical assessment of blood and possibly CSF as well as serial MRI imaging.

  • CSF βhCG levels should be analyzed on an instrument validated for use in CSF or on multiple instruments, and the pitfalls of testing this marker (false negative in some germ cell tumors, false positives in other conditions, lack of internationally agreed reference ranges for diagnosing germ cell tumors) should be considered when interpreting the results.

Open access

Raluca Maria Furnica, Julie Lelotte, Thierry Duprez, Dominique Maiter and Orsalia Alexopoulou

Summary

A 26-year-old woman presented with severe postpartum headaches. Magnetic resonance imaging (MRI) revealed a symmetric, heterogeneous enlargement of the pituitary gland. Three months later, she developed central diabetes insipidus. A diagnosis of postpartum hypophysitis was suspected and corticosteroids were prescribed. Six months later, the pituitary mass showed further enlargement and characteristics of a necrotic abscess with a peripheral shell and infiltration of the hypothalamus. Transsphenoidal surgery was performed, disclosing a pus-filled cavity which was drained. No bacterial growth was observed, except a single positive blood culture for Staphylococcus aureus, considered at that time as a potential contaminant. A short antibiotic course was, however, administered together with hormonal substitution for panhypopituitarism. Four months after her discharge, severe headaches recurred. Pituitary MRI was suggestive of a persistent inflammatory mass of the sellar region. She underwent a new transsphenoidal resection of a residual abscess. At that time, the sellar aspiration fluid was positive for Staphylococcus aureus and she was treated with antibiotics for 6 weeks, after which she had complete resolution of her infection. The possibility of a pituitary abscess, although rare, should be kept in mind during evaluation for a necrotic inflammatory pituitary mass with severe headaches and hormonal deficiencies.

Learning points:

  • The possibility of a pituitary abscess, although rare, should be kept in mind during evaluation for a necrotic inflammatory pituitary mass with severe headaches and hormonal deficiencies.

  • In a significant proportion of cases no pathogenic organism can be isolated.

  • A close follow-up is necessary given the risk of recurrence and the high rate of postoperative pituitary deficiencies.