"False-Localizing Signs"
"False-Localizing Signs"
Neurological signs may be described as "false-localizing" when their appearance reflects pathology distant from the expected anatomical locus. The classic example, and probably the most frequently observed, is abducens nerve palsy (unilateral or bilateral) in the context of raised intracranial pressure, presumed to result from stretching of the nerve over the ridge of the petrous temporal bone. Many false-localizing signs occur in the clinical context of raised intracranial pressure, either idiopathic (idiopathic intracranial hypertension [IIH]) or symptomatic (secondary to tumor, hematoma, abscess).
A brief topographical overview of false-localizing signs (more details may be found in specific entries) includes:
- Motor system:
Kernohan’s notch syndrome: false-localizing hemiparesis Cerebellar syndrome with anterior cerebral artery territory infarction damaging frontocerebellar pathways
Brainstem compression causing diaphragm paralysis
- Cranial nerves:
Proptosis with middle cranial fossa tumor
Oculomotor (III) nerve palsy with contralateral supratentorial lesion
Divisional oculomotor nerve palsy with brainstem or subarachnoid space pathology
Trochlear nerve palsy with IIH Trigeminal nerve palsy with IIH Abducens nerve palsy with IIH Facial nerve palsy with IIH
Vestibulocochlear nerve dysfunction with IIH
- Spinal cord and roots:
Foramen magnum/upper cervical cord lesion causing hand muscle wasting ("remote atrophy")
Lower cervical/upper thoracic myelopathy producing midthoracic girdle sensation
Urinary retention with rostral spinal cord compression Radiculopathy with IIH, may even mimic Guillain-Barré syndrome
References
Larner AJ. False localizing signs. Journal of Neurology, Neurosurgeryand Psychiatry 2003; 74: 415-418
Larner AJ. A topographical anatomy of false-localizing signs. Advances in Clinical Neuroscience & Rehabilitation 2005; 5(1): 20-21
Cross References
Abducens (VI) Nerve palsy; Divisional palsy; Girdle sensation; Kernohan’s notch syndrome; Oculomotor (III) nerve palsy; Proptosis; Urinary retention
