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Patient has visual field defects but no changes in vision
A 61-year-old white male was referred to our clinic by his optometrist for evaluation of a bilateral left superior quadrantopic visual field defect. The patient reported no changes in vision and was not aware of any areas missing from his field of vision. He denied any headaches or double vision.
The patient’s past ocular history was negative. His family ocular history was positive for glaucoma. His family medical history was positive for diabetes, colon/rectal cancer and stroke. His past medical history was positive for type 2 diabetes with diabetic neuropathy and Charcot’s joints in his feet, hypertension, hyperlipidemia, atrial fibrillation and colon cancer; his colon had been resected more than 10 years previously.
The patient was allergic to penicillin, cephalosporins and carbapenems. His medications included aspirin, digoxin, diltiazem, furosemide, glyburide, lisinopril, losartan-HCTZ, metformin, metoprolol, simvastatin, warfarin and potassium.
Kristen Lambert
Leonid Skorin
His corrected distance visual acuity was 20/25+1 (pinholed to 20/20-1) OD and 20/20 OS. His corrected near visual acuity was 20/25 OD and 20/20 OS. His pupils were equal, round and reactive to light without relative afferent pupillary defect. Extraocular muscle movements were full with no restrictions, and cover tests at distance and near with correction were both orthophoric. Amsler grid testing was normal with no scotomas or metamorphopsia in either eye.
Pachymetry was 635 μm OD and 606 μm OS. Intraocular pressure was measured at 21 mm Hg OD and 22 mm Hg OS, with an Icare tonometer (Icare USA). A Humphrey central 30-2 threshold visual field test confirmed a left superior homonymous quadrantopsia with overlay of other visual field defects including superotemporal and inferonasal changes in the right eye and superonasal changes in the left.
Slit lamp examination of the anterior segment was unremarkable. No eyelid ptosis was present, and only trace nuclear sclerosis was noted in both eyes. Ciliary body was visible 360 degrees with no synechiae or pigment in either eye with gonioscopy. A dilated fundus exam revealed healthy optic nerves without neovascularization of the disc and cupping of 0.4 OD and 0.5 OS. The maculae were flat without edema in both eyes, and the vitreous appeared to be within normal limits in both eyes. Peripheral retinas were flat without holes or tears 360 degrees, and there was no evidence of diabetic retinopathy in either eye. Optical coherence tomography of the maculae and optic discs were performed, and no edema or nerve fiber layer depression was present.
Magnetic resonance imaging (MRI) of the brain with and without gadolinium was ordered and performed 4 days later.
Humphrey central 30-2 threshold visual field test of the right eye shows left superior homonymous quadrantopsia with overlay of superotemporal and inferonasal changes.
Images: Lambert K
Humphrey central 30-2 threshold visual field test of the left eye shows left superior homonymous quadrantopsia with overlay of superonasal changes.
The patient was a glaucoma suspect due to his slightly elevated IOPs, asymmetric cupping of the discs and positive family history. We suspected the visual field changes were due in part to glaucomatous optic disc changes with overlap of neuro-ophthalmic defects from either a previous cerebrovascular accident or other neurologic lesions.
The MRI revealed a large right temporoparietal mass causing obstruction of the right temporal horn and extending around the right occipital horn into the occipital lobe and choroid plexus. The lesion measured 6.5 cm x 3.5 cm. No midline shift was apparent. There was also significant surrounding white matter edema and enhancement of the mass following gadolinium administration. The patient was notified and referred to neurosurgery for further evaluation and treatment.
Surgery scheduled
The neurosurgery consult was scheduled for 1 month following the MRI results, but the patient presented to the emergency department 5 days later because of episodes of confusion and one emetic episode earlier that day. The patient felt well during the visit, and no neurologic changes were noted, so he was discharged without further follow-up.
Surgery was scheduled for 5.5 weeks after the initial diagnosis of a brain tumor from the MRI. One week before the surgery, the patient had changes in his mental status including increased irritability and memory loss, slurred speech, incontinence and difficulty with mobility of the arms and legs. A repeat MRI of the brain showed a 1.6 cm midline shift to the left and increased surrounding edema, and the lesion now measured 7.8 cm x 4.6 cm. Neurosurgical debulking and pathological diagnosis was rescheduled for 2 days later.
During the debulking surgery, approximately 70% of the tumor was removed. The neurosurgeons decided to forego more aggressive removal of the tumor, as they thought it would cause more neurologic harm than was necessary. The pathology report indicated the tumor was a glioblastoma multiforme (GBM). Chemotherapy and radiation therapy were recommended as adjunct treatments to be initiated 3 weeks after the debulking surgery.
Left image: Axial T2 MRI with gadolinium shows a large right temporoparietal mass extending into the occipital lobe with no apparent midline shift. Significant surrounding white matter edema and enhancement of the mass is present. Right image: Axial MRI with gadolinium shows midline shift from right to left.
The patient’s condition has worsened. He has a poor prognosis and is currently in hospice care.
Description of diagnosis
GBM, or grade 4 astrocytoma, is the most aggressive of the tumors arising from glial cells in the brain. Unfortunately, these gliomas are also the most common primary brain tumors in adults, with more than 22,000 Americans diagnosed in 2010, according to the National Cancer Institute. GBM is usually found in patients between the ages of 45 and 70 years old. Due to the highly malignant nature of this tumor, patients have a poor prognosis – median survival is only 12 to 15 months even with treatment.
Brain tumors are first identified on an MRI or CT scan followed by removal of a portion of the tumor by a neurosurgeon for biopsy. If the tumor causes a mass effect, such as a midline shift, the surgeon will also often simultaneously perform a debulking surgery. The entire tumor cannot be removed surgically because this would invariably destroy healthy brain tissue, and the risk of causing neurological damage is extremely high. Surgeons must weigh the risks and benefits of removing more tissue, and most consider the surgery a success if they remove the majority of the tumor. The tumor cells extend diffusely by migrating through normal parenchyma and white matter tracks, making the rate of GBM recurrence very high. Death occurs because the tumor cells spread into regions of the brain vital for life.
Treatment
Treatment consists of removing as much of the tumor tissue as possible followed by radiation therapy and chemotherapy within 2 to 4 weeks. Current treatments are aimed at damaging tumor cell DNA or inhibiting its replication. Surgical resection is a difficult but important first step to treatment.
Lacroix and colleagues found that when 98% or more of the tumor was excised, the median survival of patients was 13 months as opposed to 8.8 months when less than 98% of the tumor was removed. Standard treatment for GBM includes radiation and chemotherapy; however, most tumor cells are at least partially resistant to these therapies.
Recent research has been aimed at discovering the gene mutations behind GBM, which may lead to more sophisticated treatments. Within the past 7 years, four subtypes of GBM have been described based on different gene expression characteristics, and specific gene mutations have been implicated.
In 2009, the U.S. Food and Drug Administration approved Avastin (bevacizumab, Genentech) for treatment of GBM. Intravenous administration of 10 mg/kg every 2 weeks was shown to shrink the tumor in 26% of those treated, with results lasting about 4 months (Snowden).