Ординатура / Офтальмология / Английские материалы / Field of Vision A Manual and Atlas of Perimetry_Barton, Benatar_2003

DISCUSSION

Field description: Bitemporal partial hemifield loss with superior arcuate defect OD. Localization: Optic chiasm, superior aspect, and right intracranial optic nerve. Pathology: Craniopharyngioma (MRI shown below).

Other features: Hemifield slide, central hypothyroidism.

Tangent screen perimetry with a 3-mm white target showed a complete temporal defect OD and nasal and inferotemporal defects OS. Hand motion was preserved except in the far temporal periphery OD.

The patient’s bitemporal defects line up at the vertical meridian, with complete temporal hemianopia OS and inferotemporal loss OD; the latter suggests that it is the superior aspect of the optic chiasm that is being compressed. In addition, he has a nasal field defect that respects the horizontal nasal meridian and arches across the vertical merid-

ian—a typical superior arcuate defect, indicating compression of the right intracranial optic nerve as well. The resulting pattern on the plot is not unlike the BMW logo.

Craniopharyngiomas likely arise from the remnants of the Rathke pouch, nests of squamous cells scattered along the infundibular stem and posterior pituitary gland. The direction of compression of visual structures is more variable than with pituitary adenomas. These tumors are heterogeneous, with cystic areas and regions of dystrophic calcification. They can occur at any age from infancy onward. Children often do not complain of visual loss and present instead with hydrocephalus and pituitary insufficiency with, e.g., growth failure, retarded sexual development, and diabetes insipidus. Treatment is difficult. Complete surgical resection is rarely possible, but radiation usually given after subtotal resection reduces the risk of tumor recurrence (112).

HISTORY AND EXAM

This 51-yr-old woman had a generalized tonic-clonic seizure. MRI demonstrated multiple lesions in the right temporal lobe, which a biopsy showed to be due to sarcoidosis. She had a left upper quadrantanopia, thought to be a complication of her biopsy. She was

maintained on low-dose prednisone for many years. On examination 7 years later, visual acuity was 20/40 OU and color vision was 9/14 OD and 8/14 OS. There was an RAPD OS, and fundoscopy showed diffuse pallor OD and bowtie atrophy OS.

DISCUSSION

Field description: Incongruous partial left homonymous hemianopia. Localization: Right optic tract.

Pathology: Sarcoidosis.

Other features: Bowtie optic atrophy OS (arrowheads).

Confrontation testing showed a left upper quadrantanopia more pronounced in the right eye to hand motions.

The dramatic incongruity appears mainly in the V4e isopter, where there is a virtually complete hemianopia OD, yet preserved perception of this target in the entire left inferior quadrant OS. Marked incongruity of the field defect (120,121), the left RAPD (122), and the presence and pattern of the patient’s optic atrophy indicate that her visual loss is due

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to damage to the optic tract, not the optic radiation. T1-weighted axial MRI showed basilar enhancement that included not only the right temporal lobe (the cause of her seizures), but also the right optic tract, hypothalamus, and pituitary stalk. Thus, her field loss is from her disease, not the biopsy.

In a series of 68 patients with neurosarcoidosis, 38% had involvement of the optic chiasm or nerve (46). The disease can also affect the brain stem, spinal cord, and meninges, with some CSF abnormality (pleocytosis or elevated protein) in 81%. MRI of the brain can show either multiple white matter lesions (43%) or meningeal enhancement (38%) (46). Chest X-ray had poor sensitivity, being normal in two-thirds of the patients in this series. Biopsy of tissue from the brain or elsewhere is usually required to make the diagnosis.

HISTORY AND EXAM

This 7-yr-old girl presented with 1 month of worsening frontal headaches. She also had double vision on rightward gaze. Visual acuity was normal OU, but there was a right

RAPD and fundoscopy demonstrated papilledema bilaterally. There was also a partial right VI nerve palsy. The remainder of the neurologic examination was normal.

DISCUSSION

Field description: Incongruous partial right homonymous hemianopia. Localization: Left optic tract.

Pathology: Hypothalamic glioma.

Other features: Twin peaks papilledema OD.

The patient’s partial hemianopia respects the vertical meridian only for the smallest (I2e) target. There is more sparing near the meridian with the larger targets, which differs in outline between the two eyes. Some of the irregularity along the vertical midline may be the result of poor fixation in a young patient, but the variability in the partial sparing with the largest (V4e) isopter seems more than attributable to fixation shift. This sparing may obscure the vertical step of the hemianopia at the bedside if only large targets such as hand motion are used. T1-weighted axial MRI showed an enhancing left hypothalamic mass with hydrocephalus. She had ventriculostomy, and histology of the resected tumor showed a glioma.

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Her right optic disk showed a special “twin peaks” form of papilledema (123). This provides a vivid demonstration of the pattern of optic atrophy with optic tract lesions. The eye with temporal field loss has some atrophy of the temporal disk, where fibers from the retina just nasal to the fovea enter the nerve, and also of the nasal disk, which is occupied by fibers from the more peripheral nasal retina. The superior and inferior disk are not atrophic because they contain the arcuate fibers from the temporal retina (the good nasal hemifield). The eye with nasal field loss has atrophy of the superior and inferior disk as well as the temporal disk, because this also contains fibers from the temporal half of the macula. The result is a bowtie pattern of optic atrophy in the eye with temporal hemianopia and a more generalized temporal atrophy in the eye with nasal hemianopia, after a tract lesion has been present for several months. Most tract lesions are masses. When such a mass causes increased intracranial pressure, only the nonatrophic portions of the optic disks can express the papilledema—hence, the edema of the upper and lower disk only in this patient’s right eye.

HISTORY AND EXAM

A 65-yr-old woman with cryptogenic hepatic failure and portal hypertension underwent a liver transplant. It was difficult to wean her off the respirator, and she was in prolonged coma. When she regained consciousness, her vision was not clear and she had trouble reading. She also had dysarthria, incoordination, increased forgetfulness, and gen-

eralized limb weakness. When assessed 4 months later, visual acuity was 20/25 OD and 20/75 OS. She had no RAPD or optic atrophy. Verbal memory was impaired. She had signs of critical care myopathy.

DISCUSSION

Field description: “Hourglass” field defects—bilateral, slightly incongruous homonymous sectoranopias abutting the upper and lower vertical meridians, sparing the field around the horizontal meridians.

Localization: Bilateral lateral geniculate nuclei, medial and lateral zones. Pathology: Central pontine myelinolysis.

Confrontation testing showed left superior quadrant central defects OU to red targets and face comparison.

These unusual “hourglass” field defects (125) represent the converse of the sectoranopia of the previous case, in bilateral combination. The similarity between the two eyes

and the steps at the vertical meridian confirm that there are bilateral postchiasmal lesions. These sectoranopias stem from dysfunction of the lateral and medial zones of the lateral geniculate nuclei. The anterior choroidal artery supplies these zones. However, here the most likely cause is myelinolysis (125). A chart review revealed a preoperative hyponatremia of 121 meq/L, which was overcorrected to 150 meq/L on the day of transplantation. Myelinolysis, or osmotic demyelination, is related to this rapid overcorrection. Pathologic studies have confirmed the vulnerability of the LGN to this disorder (126). Among transplantation procedures, myelinolysis is a risk unique to liver transplants, in which patients often run a preoperative hyponatremia related to ascites and portal hypertension (127). The patient’s field defects remained stable 1 year after surgery.

HISTORY AND EXAM

This 32-yr-old man had complex partial seizures since childhood. These were refractory to medical therapy, and at age 20 he had a right anterior temporal lobectomy, which

initially improved seizure control. He did not have any visual symptoms. On assessment for a drug study, his acuity was 20/20 OU and fundi were normal.