Quadrantanopia

Overview

•Optic radiation splits after the LGN into two bundles travelling through different lobes - focal lesions disrupt only one bundle, producing a quadrant defect rather than full hemianopia

•Meyer's loop (temporal lobe) - carries lower retinal fibres = upper visual field information; loops anteriorly through temporal lobe to lower calcarine sulcus

•Parietal fibres - carry upper retinal fibres = lower visual field information; travel superior route through parietal lobe to upper calcarine sulcus

•All post-chiasmal lesions → homonymous defects, contralateral to the lesion

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PITS mnemonic: Parietal → Inferior quadrantanopia; Temporal → Superior quadrantanopia

Causes

•Ischaemic stroke - MCA territory (parietal or temporal branches); most common cause in adults

•Craniopharyngioma - calcified suprasellar tumour from Rathke's pouch; key cause in children/adolescents; compresses optic pathways above chiasm

•Intracranial tumours - gliomas or metastases compressing temporal or parietal radiation

•Head trauma - contusion or haematoma of temporal/parietal lobes

Presentation

•Visual field loss - patient 'missing things' on one side, bumping into objects; often unaware of deficit (especially superior field loss)

•Headache - raised ICP from tumour or haemorrhage

•Neglect and visuospatial difficulties - with parietal lesions (hemispatial neglect, apraxia)

•Craniopharyngioma in children - short stature, delayed puberty, diabetes insipidus (polyuria/polydipsia) + visual field loss + declining school performance

Investigations

🥇 First-line

•formal automated perimetry (Humphrey visual field testing) - objectively maps the quadrantanopic defect

•Bedside: confrontation visual field testing - rapid quadrant screening with finger counting or red pin

•Gold standard imaging: MRI brain with gadolinium contrast - superior delineation of optic radiation lesions, craniopharyngioma, stroke

•Urgent alternative: CT head - if MRI unavailable or contraindicated, to exclude acute haemorrhage

•If craniopharyngioma suspected: endocrine profile (IGF-1, cortisol, TFTs, LH/FSH, prolactin)

Differential diagnosis

Visual field defects - localisation

Defect	Localisation	Example cause
Superior quadrantanopia (homonymous)	Temporal lobe (Meyer's loop)	MCA stroke, temporal tumour
Inferior quadrantanopia (homonymous)	Parietal lobe (superior fibres)	MCA stroke, parietal tumour
Homonymous hemianopia	Complete optic radiation or occipital cortex	MCA or PCA stroke
Bitemporal hemianopia	Optic chiasm	Pituitary adenoma, craniopharyngioma
Monocular field defect	Ipsilateral retina or optic nerve (pre-chiasmal)	Retinal lesion, optic neuritis

🎯

A quadrantanopia is always homonymous and contralateral to the lesion. If the defect is monocular or does not respect the vertical meridian, look for pathology anterior to the chiasm.

Management

•Ischaemic stroke: aspirin 300 mg; thrombolysis if within window and eligible; manage per acute stroke pathway

•Craniopharyngioma (children): neurosurgical referral for surgical resection ± radiotherapy; urgent referral to paediatric neuro-oncology MDT

•All new significant visual field defects: urgent ophthalmology and neurology review

•DVLA: patient must not drive and must notify DVLA; Estermann visual field test required to determine fitness to drive

•Low vision rehabilitation: referral to low vision clinic for aids and eccentric viewing training once acute cause managed