Quiz: Missing Since Birth

Test your understanding of this case with 11 questions.

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Case Information

Review the case details while answering questions

PATIENT DEMOGRAPHICS

34-year-old female

PRESENTING COMPLAINT

Attended for a routine eye examination; no visual symptoms were volunteered. The visual field defect was identified incidentally on testing, and the patient was unaware of any deficit.

EXAMINATION FINDINGS

Visual Acuity: OD: 6/6. OS: 6/6

Pupils: Equal and reactive, no RAPD

Fundus: Unremarkable bilaterally

INVESTIGATIONS

Humphrey 30-2 printout demonstrating a congruous homonymous inferior quadrantanopia with macular sparing

Visual Field Testing (Humphrey 30-2, both eyes): VFI: OD 93%, OS 88%. MD: OD -4.61 dB (P<1%), OS -6.77 dB (P<0.5%). PSD: OD 10.14 dB (P<0.5%), OS 10.77 dB (P<0.5%). GHT: outside normal limits, both eyes. Demonstrates a congruous, homonymous inferior quadrantanopia, with sparing of the central (macular) field in both eyes.

Axial MRI demonstrating a porencephalic cyst in the superior occipital lobe

Sagittal MRI demonstrating the cyst above the calcarine fissure, sparing the macular representation area

MRI Brain (axial and sagittal views): Demonstrates a porencephalic cyst (congenital) involving the superior part of the occipital lobe, above the calcarine fissure, with sparing of the macular representation area.

Question 1 of 11

This field defect was entirely asymptomatic and found incidentally. Given the porencephalic cyst is congenital, why might this be the case?

Asymptomatic defects always indicate the field test was unreliable

Congenital defects are often unnoticed, with no prior comparison

The defect must therefore be too small to be clinically meaningful

Congenital lesions never produce a measurable field defect

Question 2 of 11

The cyst is described as being above the calcarine fissure. Why would this cause an inferior, rather than superior, field defect?

The macula is represented exclusively above the calcarine fissure

The cuneus represents the inferior field, due to retinotopic inversion

The visual pathway crosses an extra time above the calcarine fissure

Lesions above the fissure always spare the corresponding field

Question 3 of 11

Despite a genuine, measurable bilateral field defect, no RAPD is present. Why is this expected?

RAPD only becomes apparent once VA is also reduced

RAPD localises to pre-chiasmal pathology; this defect is post-chiasmal

The absence of RAPD indicates the field result is inaccurate

RAPD is expected here and its absence is unexplained

Question 4 of 11

The field defect is highly congruous — nearly identical in both eyes. What does this specifically suggest about the lesion's location?

High congruity confirms the lesion is chiasmal, not retrochiasmal

High congruity specifically indicates an optic nerve, not cortical, lesion

Congruity has no localising value for homonymous field defects

High congruity favours an occipital, not optic tract, localisation

Question 5 of 11

Macular function is preserved in this patient, despite the extent of the field defect. Why does macular sparing occur specifically in this case?

Macular sparing here reflects incomplete, unreliable field testing

The cyst's boundaries do not extend into the macular representation area

Dual blood supply from the PCA and MCA protects the macula here

The macula cannot be affected by any congenital cortical lesion

Question 6 of 11

What is a porencephalic cyst?

A calcified, benign lesion arising from the pineal gland

An acquired cystic tumour arising from arachnoid cell rests

An inflammatory abscess cavity from an in-utero infection

A congenital, CSF-filled cavity from a destructive brain defect

Question 7 of 11

What is the most likely diagnosis?

A pituitary macroadenoma, causing bitemporal field loss

Bilateral primary open-angle glaucoma, at an early stage

Porencephalic cyst causing an inferior, macular-sparing quadrantanopia

Bilateral optic neuritis, affecting both optic nerves equally

Question 8 of 11

What feature, if present, would suggest this is NOT simply a stable, longstanding congenital finding?

Progression on serial testing, or new neurological symptoms

A visual field defect being present at all, regardless of stability

The patient being unaware of any visual difficulty

The defect affecting both eyes in a congruous pattern

Question 9 of 11

The Humphrey field printout reports a VFI of 88% and MD of -6.77dB in the left eye. What do these indices broadly represent?

Overall measures of visual field function and deviation from normal

A measure of visual acuity, unrelated to the visual field itself

A measure of pupil reactivity during the visual field test

Direct measurements of intraocular pressure at the time of testing

Question 10 of 11

Beyond reassurance, what practical safety consideration is relevant even though this field defect is stable and asymptomatic?

Whether the combined field loss meets national driving standards

Whether cataract surgery is required in either eye currently

Whether colour vision testing is needed for occupational purposes

Whether the patient requires immediate cessation of all driving

Question 11 of 11

A colleague wonders whether this could instead represent a new, acquired lesion rather than a longstanding congenital one. What would help distinguish the two?

Acquired lesions never produce a congruous, macular-sparing pattern

Congenital lesions always present with severe, symptomatic visual loss

There is no reliable way to distinguish congenital from acquired lesions

Evidence of stability on serial testing, and the specific imaging appearance