BACKGROUND: Lung cancer is the most common form of cancer and the most common cause of mortality compared to other cancers. There are 4 subtypes of brochogenic carcinoma including: squamous cell carcinoma, small (oat) cell carcinoma, large cell carcinoma and adenocarcinoma. Unfortunately, metastatis occurs with great frequency, and can occur in the brain via hematogenous spread.
CASE REPORT(S). We report a case where threshold visual fields appeared to diagnose a brain metastasis before it appeared on a a CT scan. Our patient was a 70 yo WM who took a visual field test due to cup-to disc asymmetry (.6 OD, .35 OS). His medical history was positive for for small cell carcinoma of the lung secondary to smoking (150 pack years) which was unresponsive to radiochemotherapy. In addition, the patient had uncontrolled diabetes, anemia and was status post a 4 vessel CABG, LICA stent and pacemaker placement. A Humphrey 30-2 visual field was performed. The results suggested a right, incongruous hemianopsia,which was confirmed by retesting one week later. A CT scan was ordered, but showed no evidence of metastatic disease. An MRI was not possible due to the patient's pacemaker. We repeated the fields 3 months later, obtaining the same result. The CT was repeated and showed a 2 cm mass inthe left posterior frontal lobe, as well as a 1 cm mass in the left parietal lobe, both considered to be metastatic in nature. The latter was consistent with the patient's field cut. The brain lesions were determined to be untreatable, and the patient succumbed to his illness within 2 months.
CONCLUSIONS. In this particular case, visual field testing was more reliable than CT scan in detecting a CNS lesion. In cases where brain pathology is suspected to affect the visual pathway, and when MRI testing is not possible, formal visual field testing may aid in early diagnosis.