A lump in the neck and in the petrous part of the temporal bone
Authors: Buch HN , Varughese G , Akber M , Clayton RN 
Published: May 2014

In May 1998, a 49-year-old man was referred to the endocrine clinic with long-standing low back pain and asymptomatic hypercalcaemia. There was no history of renal calculi and family history was negative. Systemic examination and blood pressure were normal. Serum calcium was 2.79mmol/litre (normal range (NR) 2.10–2.50mmol/litre) and parathyroid hormone (PTH) level was 7.5mU/litre (NR 1.0–5.5mU/litre). Renal function was normal. Xrays of lumbar spine showed severe osteopenia, which was confirmed by a dual energy X-ray absorptiometry (DEXA) scan (z score = –2.1SD). In 1977, he had undergone sub-total thyroidectomy for a thyroid nodule and the histology had shown typical features of medullary thyroid carcinoma (MTC) including amyloid formation. Plasma calcitonin values from that time could not be traced from the hospital records. An observational policy had been pursued till 1989, when, in the absence of overt disease, he was discharged.

In view of the history of MTC and the subsequent presentation with primary hyperparathyroidism, a clinical diagnosis of multiple endocrine neoplasia (MEN) 2a was made. Urinary catecholamines were normal. Fasting plasma calcitonin was 1.5 mg/litre (normal <0.08 mg/litre) and pentagastrin test (pentagastrin 0.5mg/kg is injected intravenously over 10 seconds and calcitonin measured at 2 and 5minutes; a rise in calcitonin indicates MTC) was positive indicating residual or metastatic MTC (basal calcitonin 1.0 mg/litre peaking at 8.2 mg/litre). Computed tomography (CT) scans and an isotope bone scan did not reveal metastases in liver, lungs or bones. Residual disease was suspected to be in the thyroid remnant and he was referred for a combined parathyroidectomy and completion thyroidectomy. A single parathyroid adenoma was identified in the left lower parathyroid gland and was removed. However, the thyroid remnant could not be removed as it was adherent to the trachea and attempts to remove it resulted in significant bleeding. Histology confirmed a well-defined parathyroid adenoma and serum calcium and PTH levels normalized. Following surgery the patient was lost to follow up.

In June 2000, he presented with a sudden onset of diplopia on looking to the right and paraesthesia over the right half of face. A right sixth cranial nerve palsy was confirmed. There was no objective facial sensory loss and the rest of the neurological examination was normal. CT scan showed erosion of the petrous part of the temporal bone and a magnetic resonance imaging (MRI) scan showed a lesion in the right Meckel’s cave, the appearances of which were suggestive of a schwannoma or neurofibroma. However, in view of the history of MTC and a plasma calcitonin of 4.0 mg/litre, the possibility of a secondary deposit was considered. The authors sought evidence for a neuroendocrine tumour using specific radionuclides. An octreoscan, an MIBG scan (iodine- 131-meta-iodobenzylguanidine) and a pentavalent dimercaptosuccinic acid (DMSA) scan did not show any uptake in the area where the lesion had been demonstrated on the MRI scan.

Over the following 12 months there has been no clinical or radiological progression of the lesion and the patient has remained well. Diplopia has persisted and is being successfully managed by appropriate prism lenses. The authors believe that this patient has MEN 2a syndrome and the residual MTC is likely to be in the thyroid remnant. The intracranial lesion is most probably a neurofibroma, which is known in association with MTC. As the patient remains well, an observational policy will be followed for both the residual MTC and the intracranial lesion and the neurosurgical team would consider a biopsy or removal of the intracranial lesion in the event of its clinical and radiological progression.