Walsh & Hoyt: False Localizing Symptoms and Signs of Tumors

Because of the increasing use of computed tomography (CT) scanning and magnetic resonance (MR) imaging in patients with neurologic disorders, the issue of signs that are falsely localizing is now of less practical importance. Nevertheless, these signs still may occur in patients with intracranial and orbital tumors and require some comment. There is occasionally difficulty in defining precisely what constitutes a false localizing sign, and it is often easier to indicate what should not be so considered. Gassel, in his study of false localizing signs in 250 cases of intracranial meningioma, indicated that such a sign potentially causes confusion in diagnosis by suggesting an abnormality at a distance from the actual site of the mass lesion. It is not a clinical finding that is misinterpreted. Thus, a bitemporal hemianopia associated with a posterior fossa tumor is a false localizing sign. The site of damage the optic chiasm is clear, but the localization of the initiating lesion to the chiasm will prove incorrect. On the other hand, unilateral corneal hypesthesia associated with an ipsilateral homonymous hemianopia may originate from damage to the contralateral temporal isthmus. If the corneal finding is thought to reflect an ipsilateral trigeminal neuropathy, it is an error in evaluation and not a false localizing sign. In addition, ""neighborhood"" signs should not be considered as falsely localizing, because they should be anticipated by the examiner. Thus, signs that reflect intrinsic brain stem damage are often associated with extra-axial tumors that produce brain stem compression or ischemia. Collier found false localizing signs in 12.5% of 161 consecutive cases of intracranial tumor. Cranial nerve pareses were prominent: abducens nerve paresis in 12 cases, oculomotor nerve paresis in 2 cases, facial neuropathy preceded by abducens nerve paresis in 2 cases, and eighth nerve dysfunction in 2 cases.