Trochlear Nerve Palsy (Fourth Nerve Palsy) Workup

Updated: Jun 30, 2022
  • Author: Zafar A Sheik, MD; Chief Editor: Andrew G Lee, MD  more...
  • Print

Approach Considerations

The patient’s history should be taken into consideration when considering further workup. Acquired isolated and presumed ischemic or posttraumatic fourth nerve palsy often resolves spontaneously. [20] Neuroimaging should be considered for nonisolated, bilateral, progressive, or unexplained fourth nerve palsies. If observation is elected (eg, ischemic, traumatic, congenital) but the fourth nerve palsy does not resolve, further testing including neuroimaging (eg, MRI/MRA, CT scanning of the head and orbit), along with other laboratory studies, may be indicated.


Laboratory Studies

General laboratory studies include fasting glucose and HbA1C.

Myasthenia gravis: Anti-acetylcholine receptor antibodies, anti-striated muscle antibody, anti-MuSK antibody, anti-LRP4 antibody

Thyroid eye disease: Free T4, TSH, thyroid receptor antibody, TSH-binding inhibitor immunoglobulin, anti-TPO antibodies

Giant cell arteritis: ESR, CRP, temporal artery biopsy


Imaging Studies


MRI can be used to identify lesions or inflammation that affects the parenchyma or brainstem. These lesions can include ischemia or a tumor.

MRA illustrates blood flow and can aid in identifying an aneurysm.

CT scanning of head and orbit

CT scanning can help identify disease within the orbit or skull. It is sensitive in detecting calcifications and intracranial aneurysms.