Which of the following is the most common false localizing neurological sign in assessing brain tumors
Answer is D (Diplopia): Sixth Nerve Palsy (Abducent; Lateral Rectus) producing double vision (diplopia) is the most common false localizing sign because of its long intracranial course. 'A right sided brain tumor can produce either a right sided or a left sided sixth nerve palsy as an initial sign. Thus left sided sixth nerve palsy in a right-sided brain tumor represents the infamous false localizing sign'. The most common false localizing sign is a sixth nerve palsy (diplopia). The nerve is paicularly vulnerable because of its long course' - Merritt's Neurology Brain Tumors Generalized features (Non-Localizing signs) Generalized symptoms like headache (most common generalized sign), nausea, vomiting, veigo, dizziness and non specific mental and cognitive abnormalities represent generalized features of brain tumors that do not help localize the tumor to a paicular pa of brain. Localizing /Focal signs The presence of a tumor impairs the function of the pa of the brain where it resides The nature of evolving focal neurological defecit / focal seizures serves as localizing signs for tumors in various pas of brain Unilateral papillaedema, abnormal unilateral pupil, specific aphasia, agnosias etc. can localize the tumor to a paicular pa of the brain. False Localizing Signs Neurological signs that reflect dysfunction, distant from the actual pa of the brain involved arc called False localizing signs *False localizing signs are generally produced from raised ICT and/or shift and compression of brain remote from the primary site. The most common false localizing sign is sixth nerve palsy (Lateral Rectus Palsy producing Diplopia). The sixth CN is especially vulnerable because of its long intracranial course. False Localizing signs (Brain tumors causing Raised ICT are known to produce false localizing signs) Sixth Nerve Palsy (Lateral pectus palsy) producing diplopia is the most common false localizing sign produced by compression of the abducent nerve as it passes over the petrous ridge. Ventricular dilation above midlinc in CSF obstructive lesions or posterior fossa lesions may produce false localizing signs Intellectual and Behavioral changes suggestive of primary frontal pathology An interference with veical eye movement (impaired up-gaze) which are programmed in the upper midbrain because of the dilation of posterior pa of 3rd ventricle and aqueduct Ipsilateral hcmiparesis may represent a false localizing sign when a herniating uncus compresses the contralateral cerebral peduncle against the tentorium. Coical blindness or hemianopia may occur from compression of posterior cerebral aeries with occipital infarction from herniation through the tentorial notch. Tinnitus may present as a false localizing sign as this may result from raised ICP of any cause. Hydrocephalus may lead to presonality changes, gait abnormalities and urinary incontinence suggesting false localizing signs.
Seizures
Unilateral papilloedema
Abnormal unilateral pupil
Diplopia