Common Cases: Neurological Visual Field defects
- 2. Most common field defects and their underlying conditions are: Tunnel vision in advanced retinitis pigmentosa and advanced glaucoma Altitudinal field defect in ischaemic optic neuropathy and branch retinal artery occlusion Arcuate scotoma in glaucoma
- 3. MRI of the optic nerves and the visual pathway Lesion at junction between the optic nerve and the chiasm Lesion around the optic chiasm Lesion in the optic tract Lesion in the temporal/parietal lobe Lesion in the occipital lobe Lesion resulting from inflammation of the optic disc
- 4. Remember to describe the visual field as the patient sees it. Mention if the field defect is congruous (behind the lateral geniculate body) or incongruous (in the optic tract). Look for other neurological signs such as hemiplegia from cerebrovascular accident.
- 5. The peripheral visual fields are normal in both eyes. There is a right central scotoma (revealed by testing the central field with a red pin). Examine the patient's fundus for any evidence of papillitis or optic atrophy. Check for RAPD.
- 6. The patient has a right central scotoma and superior temporal field defect in the left eye. The findings suggest a lesion in the junction between the optic nerve and the chiasm on the side with the central scotoma.
- 7. It is caused by compression of the knee of Wilbrand which is a loop of inferior nasal fibers. This enters the contralateral optic nerve for a short distance before traveling in the optic tract. Examine the fundi for optic atrophy on the side with central scotoma and possible papilloedema on the other side. Look for causes. The most common causes are meningioma (the patient may have proptosis ) and a prefixed pituitary tumor (the patient may have signs of hypopituitarism or Acromegaly).
- 8. There is bitemporal hemianopia which obeys the midline (the hemianopia may be worse in one eye than the other or denser superiorly or inferiorly). This suggests a lesion in the optic chiasm. - The hemianopia may be subtle and revealed only by comparing two red objects in each hemifield. The red color in the temporal field appears washed out. - If the hemianopia does not obey midline consider pseudo-bitemporal hemianopia such as bilateral sectoral retinitis pigmentosa, tilted discs or bilateral infero-temporal retinoschisis. Examine the fundi for any such changes. - Examine for features of pituitary abnormalities such as acromegaly, pan- hypopituitarism (smooth skin and absence body hair in male) - Look for any scar suggestive of pituitary operation.
- 9. There is left incongrous (the shape of the defect is different in the two half fields) homonymous hemianopia The lesion is in the right optic tract). Lesions associated with optic tract are often associated with contralateral pyramidal signs (due to damage to the cerebral peduncle) such as spasticity.
- 10. Left superior homonymous quadrinopia Left inferior homonymous quadrinopia The optic radiation is found in both the temporal lobe and the parietal lobe. - In a patient with a left superior homonymous quadrinopia, the lesion is likely to be in the temporal lobe. - Left inferior homonymous quadrinopia is seen in lesion of the parietal lobe.
- 11. Test the patient for Gertmann's syndrome ? Gertmann's syndrome which is seen in lesion of the dominant parietal lobe which is usually the left in right handed person Failure of patient's ability to calculate, name fingers and tell left from right
- 12. Perform the opto-kinetic drum test for evidence of parietal lobe lesion ? There is impaired pursuit movement to the side of the lesion.
- 13. Astereognosis (failure to tell an object through touch) Joint position sense loss Loss of two point discrimination
- 14. Alternatively touching the patient's right then his left hand and then touching the two hand together (with patient's eyes closed). If the patient has sensory inattention, he would notice only one side being touched when you touch both his hands simultaneously.
- 15. Normal opticokinetic nystagmus with smooth pursuit movement. Abnormal opticokinetic nystagmus with small saccadic movement replacing the smooth pursuit movement.
- 16. Left homonymous hemianopia left homonymous hemianopia with macular sparing Lesion of the optic radiation as it approaches the occipital cortex can lead to homonymous hemianopia which is often congruous. Lesion of the occipital cortex may produce macular-sparing homonymous hemianopia this is most often seen in cerebrovascular accident involving the posterior cerebral artery. Testing for macular sparing is done by moving a red target form the non-seeing field into the seeing field. If the red pin is noticed before it crosses the mid- line, macular sparing is present.
- 17. History: Acute (vascular disorder) or Chronic (space-occupying lesion) History of CVD, DM and smoking Examination: Cardiovascular examination for hypertension, atrial fibrillation, cardiac disorders and carotid artery disease. Neurological examination for raised ICP Blood tests for full blood count for hyperviscosity conditions such as polycythemia, ESR (? Vasculitis) CT scan for CVA, space occupying lesion. Chest X-ray if there is evidence of cerebral space- occupying lesion.