Intermediate
Technical
IVT
fourth nerve palsy
Trochlear nerve paralysis causing superior oblique muscle weakness and vertical diplopia.
Full Definition
Paralysis of the fourth cranial nerve (trochlear nerve) resulting in weakness of the superior oblique muscle. Presents with vertical and torsional diplopia that worsens when looking down and toward the affected side. Patients often adopt a compensatory head tilt away from the affected eye. Can be congenital or acquired due to trauma, microvascular disease, or increased intracranial pressure. The most common isolated cranial nerve palsy.
Usage
Usage note: Hyphenate when used as an adjective; write out 'fourth' rather than using '4th'.
In Context
- "The patient's right fourth nerve palsy was confirmed by the characteristic head tilt and Parks-Bielschowsky testing." — Neuro-ophthalmology evaluation
- "Congenital fourth nerve palsy often presents with longstanding head tilt and compensated diplopia." — Pediatric ophthalmology report
Also known as
trochlear nerve palsy
superior oblique palsy
Don't confuse with
sixth nerve palsy
third nerve palsy
skew deviation