Pituitary adenoma presenting as acute onset isolated complete third cranial nerve palsy without vision changes

Abstract

We report a case of isolated unilateral complete pupil involving third cranial nerve palsy due to pituitary adenoma with parasellar extension into the right cavernous sinus. The patient was referred to us from neurosurgery with sudden onset binocular vertical diplopia with complete ptosis, and mild right-sided headache of 5-day duration. Ocular examination revealed pupil involving third cranial nerve palsy in right eye while rest of the examination including automated perimetry was normal. MRI brain with contrast revealed a mass lesion with heterogenous enhancement in the sella suggestive of a pituitary macroadenoma with possible internal haemorrhage (apoplexy). In addition, the MRI showed lateral spread to the right cavernous sinus which was causing compression of the right third cranial nerve. The patient was systemically stable. This report highlights a unique case as the lesion showed a lateral spread of pituitary adenoma without compression of the optic chiasm or other cranial nerves.

Background

Pituitary adenomas usually present with loss of vision and visual field defects, typically, bitemporal hemianopia secondary to axial vertical spread and compression of anterior visual pathways, that is, optic nerves and optic chiasm.¹ Uncommonly, these tumours might present as isolated acute ophthalmoparesis or rarer still, as an isolated ocular motor nerve palsy. The third cranial nerve may be involved due to the gradual spread of the adenoma laterally into the cavernous sinus, leading to compression of the cranial nerves.² On the other hand, acute involvement of the third cranial nerve due to pituitary adenoma might occur secondary to pituitary apoplexy which might cause an acute enlargement of the pituitary tumour and compression of the adjoining cranial nerves. This could be a life-threatening condition. Prompt diagnosis and immediate intervention is essential in such cases.

Case presentation

A 50-year-old man was referred to us from neurosurgery for evaluation for sudden onset drooping of the right eyelid of 5-day duration, associated with mild right-sided headache. He complained of vertical double vision on elevating the eyelid. He denied any visual complaints. He was diagnosed to have hypertension 7 years ago and had paralytic stroke 7 years prior. At the time of presentation, patient was systemically stable. On examination, his best corrected visual acuity (BCVA) was 20/30, N6 in the right eye (RE) with +2.25/–0.75 Diopter (D) cylinder at 70⁰ and a near add of +1.75 D and 20/20, N6 in the left eye (LE) with +2.00/–0.50 D cylinder at 90⁰ and a near add of +1.75 D. Colour vision was normal (17/17 correct plates) on Ishihara chart in both eyes. He had complete ptosis with −4 limitation of adduction, elevation and depression in the right eye (figure 1). Ocular movements in the left eye were full in all directions of gaze. On cover test, there was 35 prism dioptre (PD) right exotropia with 20 prism dioptre right hypotropia in primary gaze. Corneal sensitivity and facial sensations were normal in both eyes. The pupil in the right eye was 6.5 mm in size, sluggishly reacting to both direct and consensual light reflex. The pupil in the left eye was 3.5 mm with brisk direct and consensual reactions suggestive of lack of relative afferent pupillary defect in the right eye. Fundus examination in both eyes revealed a moderate size disc with cup:disc ratio of 0.5, healthy rims and normal retina (online supplementary figure 1a). The patient had already undergone MRI brain and orbits with MR angiogram brain (described below).

Figure 1.

Pre-operative 9-Gaze photograph of the patient showing −4 limitation of adduction (white arrow), elevation (white triangle) and depression (white asterix) in the right eye after elevating the right eyelid. There was associated complete ptosis in the right eye and the photos were taken with the lid completely elevated by the examiner. In addition there was anisocoria with right eye pupil being larger and sluggishly reacting to light (appreciated in the central photos showing the primary gaze).

Investigations

Automated perimetry performed using the 24–2 Swedish Interactive Thresholding Algorithm-FAST (SITA- FAST) strategy (Humphrey visual fields, Carl Zeiss Meditec) which were essentially full in both eyes (online supplementary figure 1b). MRI brain with contrast and magnetic resonance angiography (MRA) revealed a focal lesion measuring 21×13×13 mm within the sella with parasellar extension involving the right cavernous sinus (figure 2A, B). The lesion was slightly hyper-intense on T1-weighted and T2-weighted images and showed intense contrast enhancement. In addition, there was internal hypodensity suggestive of haemorrhagic contents (figure 2B). The lesion was suspected to be a pituitary macroadenoma with apoplexy. Optic chiasm was normal. Chronic lacunar infarcts were noted in the right thalamus and right lentiform nucleus and there was an incidental cavernoma in the pons. Patient’s serum electrolytes, glucose, prolactin, thyroid hormone and growth hormone levels were within normal limits.

Figure 2.

(A) Axial T1-weighted post contrast scan of the MRI depicting a hyperintense sellar mass with lateral extension, compressing the right cavernous sinus (white asterix). (B) Coronal T1-weighted post contrast scan of the MRI depicting the heterogenenous sellar mass extending laterally to the right (white arrow) but sparing the chaism superiorly (yellow arrow). The intrinsic hypointense signal inside the lesion is possible suggestive of the pituitary apoplexy that might have precipitated the acute change (yellow asterix).

Diagnosis

A diagnosis of isolated right complete pupil involving third cranial nerve palsy secondary to lateral spread of pituitary macroadenoma into the right cavernous sinus with pituitary apoplexy was made.

Treatment

The patient underwent endoscopic trans-nasal trans-sphenoidal resection of the pituitary macroadenoma.

Outcome and follow-up

On 1 month follow-up visit, the patient complained only of slight blurring of vision during near work. His best corrected visual acuity was 20/20, N6 and colour vision was normal on Ishihara chart in both eyes. He had mild ptosis in the right eye with −1/2 limitation of elevation and adduction (figure 3). On prism bar cover test, there was 4 PD exotropia for distance and near. His fundus examination and visual fields were normal (online supplementary figures 2a, b).

Figure 3.

Postoperative 9-gaze photograph showing marked improvement in the postoperative motility. Post-operatively the patient had only – 1/2 limitation of adduction (white arrow), elevation (white triangle) and depression (white asterix) in the right eye. There was marked improvement in the ptosis with only mild residual ptosis in the right eye.

Discussion

Our case reports an unusual presentation of a pituitary macroadenoma presenting with a lateral spread rather than the usual axial (vertical) spread. There are prior reports in literature of pituitary adenoma causing isolated ophthalmoparesis, although rare.^3–8 Our patient presented with an acute onset pupil involving third cranial nerve palsy which usually warrants immediate imaging to look for compressive aneurysm in the subarachnoid space. Uncommonly these patients might have tumours in the course of the third nerve such as schwannomas,⁹ cryptogenic cavernous sinus menigiomas¹⁰ or sellar tumours with lateral spread.² Of these, pituitary adenoma is a rare cause and has been reported to be in about 14% cases.¹¹ Usually these cases are advanced and have concomitant vision loss.^{12 13} Lau et al reported a case of a pituitary adenoma presenting with complete, bilateral oculomotor nerve palsies, with minimal loss of visual fields, and intact abducens and trochlear nerves.³ In that case visual acuity in both eyes was 6/18, which persisted even after the surgical excision of the tumour. Uncommonly these patients might present with isolated third cranial nerve palsy and no vision/ visual field defects like our case.⁴ Varma et al reported a case similar to ours, which presented with acute, partial pupil involving third nerve paresis without affecting vision or other cranial nerves.⁴ The ptosis and the ophthalmoplegia were partial however, and following post-transsphenoidal resection of the tumour, there was complete recovery of the paresis. Saul et al reported five cases of third nerve palsy as the presenting sign of pituitary adenoma.⁵ Out of these, only one was reported to be associated with temporal field defect. Four cases had partial third nerve paresis while only one had complete palsy. Cano et al reported one case of intermittent third nerve palsy secondary to pituitary adenoma that was associated with pain, rhinorrhoea and lacrimation.⁶

Our patient had an acute onset of presentation, with only mild headache, but with complete third nerve palsy. It was also unique in that the vision was almost unaffected, and the visual fields were completely normal. Possible hypothesis for such a presentation in an expanding sellar mass is believed to be anatomical location of the nerve in the cavernous sinus.¹⁴ The oculomotor nerve is the located more medially than other nerves in the lateral wall of the cavernous sinus and lies at the level of the pituitary gland which predisposes the third cranial nerve to be affected earlier than others in this mechanism of spread.^{3 14} Further, given the acute presentation and presence of heterogenous appearance of the lesion in our patient we believe that the acute compression effect was secondary to acute apoplexy. Timely intervention with early resection of the pituitary macroadenoma led to a good recovery in ophthalmoparesis and good residual visual function.

Learning points.

• In an acute onset isolated pupil involving third cranial nerve palsy, apart from aneurysm of posterior communicating artery, consider mass lesions in close vicinity of the nerve in differential diagnosis.

• Pituitary adenomas especially with apoplexy might present as acute onset isolated third cranial nerve palsy without vision changes.

• Consider MRI brain with contrast in addition to MR angiography in the workup of these cases.