Chiari I Malformation with Concomitant Nonfunctioning Pituitary and Adrenal Tumors

Introduction:
Chiari I malformation (CM1) is a rare finding with an incidence ranging from 3.3 to 8.2 per 100000. CM1 has been described with growth hormone secreting pituitary adenomas, and with EPAS1 gain-of-function mutation syndrome with multiple paragangliomas/pheochromocytomas, somatostatinoma, and polycythemia. There is only one case report in the literature describing a nonfunctional pituitary adenoma with CM1. We describe the first reported case of a patient with CM1 with concomitant nonfunctional pituitary and adrenal incidentalomas.

Case Description:
A 45-year-old female with history of diet-controlled diabetes and HTN presented with a two week history of bilateral upper extremity weakness and paresthesia, along with gait instability. She had reduced motor power in the upper extremities on physical exam. MRI cervical spine demonstrated a cervicothoracic syrinx, cerebellar tonsillar ectopia consistent with CM1. MRI brain showed diffuse enlargement of the pituitary gland measuring 16 x 14 x 13 mm bulging into the suprasellar cistern and minimally abutting the inferior aspect of the optic chiasm. MRI lumbar spine revealed a left adrenal gland nodule measuring 1.5 x 2.0 cm.

Endocrine hormonal evaluation showed normal prolactin, follicle stimulating and luteinizing hormone, estradiol, free T3, free T4, and IGF-I levels. Aldosterone level was high in supine position with normal plasma renin activity initially with normal levels on repeat testing. Plasma free metanephrine, normetanephrine, testosterone levels were also normal. Patient was started on dexamethasone in anticipation of surgery.

Patient underwent suboccipital craniectomy, C1 laminectomy, coagulation of cerebellar tonsils and expansile duraplasty for CM1. Patient did well postoperatively and dexamethasone was tapered off. Postoperative follow up after patient had been off steroids for three weeks showed normal levels of all pituitary and adrenal hormones, including normal dexamethasone suppression test.

Discussion:
While CM1 is a rare finding, pituitary adenomas are relatively common. In cases of concomitant occurrence of CM1 and growth hormone secreting pituitary adenoma, over-secretion of growth hormone has been proposed as a mechanism to precipitate symptoms of CM1 by causing hypertrophy of connective and ligamentous tissue in the skull base and of the cranio-cervical canal. Our patient had normal IGF-1 levels with a nonfunctional pituitary adenoma raising the question whether there is some other underlying mechanism, possibly a genetic predisposition, that contributed to the concomitant occurrence of CM1 with pituitary and adrenal tumors. Whether these tumors become functional in the future remains to be seen.