Pituitary macroadenoma with invasion into cavernous sinus, cranial nerve palsies
A 68-year-old woman with a past medical history significant for stable hypertension and hyperlipidemia managed easily with drug therapy presented with several weeks of worsening headaches and diplopia.
Physical exam revealed a non-obese woman with anisocoria with the right pupil dilated and slightly less reactive to light than the left pupil. She also had a complete right eye ptosis and inability of her right eye to look laterally. These findings were consistent with oculomotor (CN III) and abducens (CN VI) nerve palsies. The remainder of her cranial nerve (CN) exam was normal.
The combination of CN III and VI palsies raised the concern of a pituitary adenoma with right cavernous sinus invasion. She had no findings of acromegaly or Cushingâ€™s syndrome; specifically, no central obesity or purple striae. Formal visual field exam was intact. An MRI of the sella with gadolinium revealed a 2-cm x 1.3-cm x 1.5-cm heterogeneously enhancing mass in the sella with lateral extension into the right cavernous sinus. The pituitary stalk was displaced to the left. The lesion encased and mildly narrowed the right internal carotid artery (figure 1). Her optic chiasm was unaffected.
She was immediately treated with oral steroids, which resulted in improvement of her CN III palsy with resolution of her right eye ptosis and anisocoria, but she was still unable to abduct her right eye on lateral gaze (right CN VI palsy; figure 2). Endocrinology evaluation while hospitalized showed a thyroid-stimulating hormone 1.21 mU/mL, total T4 7.9 mcg/dL, T3 uptake 39.2%, prolactin 8.2 ng/mL, follicle-stimulating hormone 4.5 mIU/mL, luteinizing hormone 0.3 mIU/mL, growth hormone 0.6 ng/mL, insulin-like growth factor I 127 ng/mL, adrenocorticotropic hormone 87 pg/mL, and random cortisol 18 mcg/dL. These results revealed a nonfunctioning pituitary macroadenoma with a slight increase in serum adrenocorticotropic hormone, but a urinary-free cortisol collected after discharge from the hospital was normal at 26 mcg for 24 hours.
One month later, she underwent an uneventful transsphenoidal pituitary adenoma debulking. Immunohistochemistry of the tumor was positive for synaptophysin and adrenocorticotropic hormone with rare prolactin staining cells. The patient responded well postoperatively and was discharged 72 hours after her procedure with a persistent right CN VI palsy. She will continue to have close follow-up with neurology, neurosurgery and endocrinology. Residual tumor remains within the right cavernous sinus because it is not accessible by transsphenoidal surgery. If growth is documented, the patient will be evaluated for external beam radiation therapy.
Photos courtesy of: Stephanie L. Lee, MD, PhD
Complication of pituitary adenomas
Pituitary adenomas account for 10% to 15% of all intracranial neoplasms and are normally a tumor of the adult population. Most pituitary adenomas are less than 1 cm and defined as microadenomas. The prevalence of pituitary macroadenomas with a diameter greater than 1 cm is estimated to be approximately 0.2%. The bulk of pituitary macroadenomas (about 80%) are nonfunctioning tumors. These tumors are clinically silent and present when they produce symptoms because of mass effect. Nonsecreting pituitary macroadenomas can present with a diverse array of symptoms that can be predicted based on the direction of growth.
Ocular CN palsy is a rare complication of pituitary adenomas and occurred in 59 of 1,000 patients in one large series of pituitary macroadenomas with lateral extension into the cavernous sinus. The pituitary gland is separated from the cavernous sinus by dura. The cavernous sinus receives blood from the middle cerebral vein, the sphenoparietal sinus and the superior ophthalmic vein and is drained by the superior and inferior petrosal sinuses. The internal carotid artery (carotid siphon) and CN VI pass through the sinus while CN III, IV, V1 and V2 are located within the lateral dural wall of the cavernous sinus (figure 3).
The oculomotor nerve (CN III) contacts nerve fibers that innervate the levator palpebrae superioris and most of the extraocular muscles that control eye movement, including the superior rectus, medial rectus, inferior rectus and inferior oblique muscles but not the superior oblique and lateral rectus muscles. The nerve also carries parasympathetic fibers to the ciliaris and sphincter pupillae muscles that control pupillary constriction to light. Injury of CN III results in drooping of the upper eyelid (ptosis), inability to constrict the pupil to light and ophthalmoplegia.
The order of injury of the CNs in the cavernous sinus by lateral extension of macropituitary adenoma is CN III, CN VI, CN IV and then CN V. Observational studies have revealed that CN III palsy from a pituitary adenoma presents initially with mydriasis, followed by limitation of gaze and, lastly, ptosis. After surgical resection of the adenoma, patients tend to improve in the reverse order in which the symptoms developed. Recovery of CN III palsy can be slow because the oculomotor nerve is easily injured by stretching or compression.
Isolated abducens nerve palsy
Although much less frequent, isolated abducens nerve palsy (CN VI), which controls the lateral rectus muscle, has been reported. Occasionally, such as in our patient, CN III and CN VI palsy are involved. The abducens nerve traverses the cavernous sinuses and runs alongside the internal carotid artery (figure 3). The nerve then enters the orbit through the superior orbital fissure and innervates the lateral rectus muscle of the eye. The abducens nerve is vulnerable to injury because of its close proximity to the internal carotid artery and the sella turcica.
It is very rare to have an isolated trochlear nerve (CN IV) palsy and dysfunction of the superior oblique muscle from pituitary tumors. Because of its proximity to the other CNs, usually there are other concurrent CN deficits. Similarly, CN V palsy is unusual, as the ophthalmic branch of the trigeminal nerve (CN V1) navigates through the superior orbital fissure and carries sensory information to the upper portion of the face, eyelid and cornea. When CN V1 palsy from a pituitary tumor is present, it implies more extension invasion of the tumor into the lateral dural wall of the cavernous sinus (figure 3) that is not in the same level as the pituitary gland.
When caused by a pituitary adenoma, management of ocular CN palsy is removal of the tumor. Many pituitary tumors with cavernous sinus invasion and CN palsies are associated with apoplexy and can be initially treated with high-dose glucocorticoids. Transsphenoidal resection is currently the widely accepted surgical approach. Recovery from CN function is directly correlated to the earlier timing of tumor resection. The average recovery time for isolated CN III palsy or combined CN III and CN VI palsy ranges widely from 36 days after trans-sphenoidal surgery to as long a one year. Thus, prompt evaluation, diagnosis and management of the pituitary tumors are advised to avoid permanent visual impairments.
Karen Choong, MD, is a Fellow in Endocrinology, and Stephanie L. Lee, MD, PhD, is Associate Professor of Medicine and Associate Chief, both in the Section of Endocrinology, Diabetes and Nutrition, Boston Medical Center.
For more information:
- Dekkers OM. J Clin Endocrinol Metab. 2008;93:3717-3726.
- Kim SH. J Clin Neurosci. 2007;14:1158-1162.
- Vance ML. Endocr Pract. 2008;14:757-763.