Pituitary adenomas (PAs), also known as pituitary neuroendocrine tumours (PitNET), are usually benign tumours of the anterior lobe of the pituitary gland. They constitute the third most common intracranial neoplasm. Prolactin-secreting pituitary adenomas are the most common type of pituitary tumour, in which dopamine agonists are the first-line treatment. However, in selected cases surgery or even radiotherapy may be required [1].
On 22 March 2022, a 59-year-old male patient, a truck driver, was admitted to the endocrinology department due to hyponatraemia, diarrhoea, and vomiting. Magnetic resonance imaging (MRI) of the brain revealed a pituitary macroadenoma 20 × 20 × 18 mm. The tumour’s growth extended beyond the sella turcica and had discreetly infiltrated other vital brain structures, including the adjacent vessels.
The patient was diagnosed with secondary adrenocortical insufficiency and hypothyroidism caused by a pituitary tumour. Ophthalmic examination revealed distance visual acuity for both eyes of 1.0 in the decimal scale on the Snellen chart and near visual acuity of 0.5 on the Jaeger chart. Intraocular pressure was 16 mmHg in both eyes. The kinetic visual field (Goldmann perimeter, Haag Streit, Switzerland), was normal with III-4e isopter. Static visual field (Octopus, Haag-Streit, Switzerland) was not typical for pituitary macroadenoma pattern changes, such as bitemporal homonymous hemianopia in the visual field, because the relative scotomata were presented in both hemifields in both eyes. However, the most affected was the lower temporal quadrant in the left eye (LE). The retinal sensitivity was above normal in the right eye (RE) and slightly below normal in the LE.
Optical coherence tomography (OCT) revealed significant thickness loss of the ganglion cell complex (GCC) in the nasal hemi-macula in the RE and in the upper nasal sector in the LE. The retinal nerve fibre layer around the optic nerve head was normal in both eyes. Photopic electroretinography (ERG), (RETeval, LKC, USA) with sensor strips electrodes was performed. The photopic negative response (PhNR) was normal, while b-wave amplitude was decreased in both eyes (Fig. 1).
The pituitary macroadenoma was removed by endoscopic endonasal surgery in August 2022.
One month after the operation, distance and near visual acuity remained stable in both eyes, and kinetic visual field was normal. Significant improvement was noted in the static visual field of both eyes. The remarkable increase in GCC of the nasal hemi-macula in the RE and recovery to normal GCC in the LE was observed. Significant improvement of b-wave amplitude and PhNR was recorded (Fig. 1).
Visual field defects are the most common clinical manifestations of pituitary adenomas.
Because pituitary tumour and optic chiasm position vary and different degrees of compression may occur, various types of visual field defect may be present, such as central, paracentral defect, or most typical — homonymous hemianopia [2].
GCC loss in the presented patient had a typical pattern, which was thinning in the nasal hemi-macula.
In electroretinography, the photopic negative response (PhNR) is a negative wave that follows the photopic b-wave and can be used for assessing the degree of damage in GCC in patients with compressive optic neuropathy. The PhNR has prognostic value in the preoperative assessment of chiasmal compression and for predicting postoperative visual acuity.
OCT measures structural changes in the GCC, while PhNR reflects functional changes. The PhNR has several practical advantages. It does not require refractive correction, clear ocular media, or exact foveal fixation because it is elicited by a strong flash [3].
In the literature, visual field defects, GCC, and retinal nerve fibre layer loss due to pituitary adenomas are well described [4, 5].
Additionally, microperimetry and contrast sensitivity test were presented as non-invasive diagnostic investigations adjunctive to MRI, which facilitated detection of early chiasmal compression caused by pituitary adenomas [6].
To our knowledge, the are no reports correlating visual field loss with GCC loss and PhNR in patients with pituitary adenomas.
The correlation with the above parameters could predict the visual outcomes after pituitary adenoma surgery and could help decision-making in difficult and unclear cases.
Compression of the optic chiasm by pituitary adenoma can lead to visual impairment. Normal visual acuity and untypical changes for pituitary adenoma in the static visual field may not indicate optic nerve compression by a pituitary tumour. In this case, GCC revealed typical pattern changes in the nasal hemi-macula due to compression of the optic nerve by pituitary macroadenoma. Photopic ERG with PhNR was also helpful in the assessment of retinal dysfunction. The function of the ganglion cells was not selectively impaired, although the function of the inner layers of the retina was abnormal due to microvascular circulatory disorders caused by pituitary tumours.
Ethics statement
The examinations were conducted ethically in accordance with the World Medical Association Declaration of Helsinki and were approved by the Ethics Committee of the Medical University of Silesia Katowice, Poland, number PCN/CBN/0022/KB1/124/21.
Author contributions
M.S.-K. — study conception and design, data collection, manuscript preparation; D.P.-W. — electrophysiological data interpretation, manuscript preparation and revision; E.M.-K. — analysis and interpretation of results, ophthalmic examination interpretation, revision of the manuscript; B.K.-K. — data collection, analysis and interpretation of endocrinological examinations, revision of the manuscript.
Acknowledgments
None.
Conflict of interest
The authors have no conflicts of interest to disclose.
Funding
The manuscript was supported by a research grant from the Medical University of Silesia (Grant No. PCN-1-080/N/2/K).
