213 - CN III Palsy and Nothnagel Syndrome in a patient with Vascular Risk Factors

Nothnagel Syndrome secondary to microvascular ischemia involving the right midbrain and cerebral peduncle.

Case Description: An 80-year-old man presented with acute diplopia and imbalance. Exam revealed a dilated, minimally reactive right pupil with limited extraocular motion (EOM), ptosis due to affected levator palpebrae, and left-sided ataxia MRI showed subacute infarcts in the right thalamus, medial midbrain, and cerebral peduncle. Following initial admission, dual antiplatelet therapy was initiated and blood pressure monitored. Once stabilized in the acute setting he was discharged to inpatient rehab with the goal of returning to baseline activity. Prior to admission he noted limited balance issues

Results: At admission, the patient required moderate assistance for stairs and uneven surfaces. Pupillary reaction and diplopia improved each day. By discharge (day 11), he progressed to supervision-level support with notable improvement in mobility, pupillary function and EOM.


Discussions:

Nothnagel Syndrome is a rare midbrain syndrome, often underdiagnosed due to its complex presentation. It arises from lesions affecting the CN III fascicle and superior cerebellar peduncle. Though non pupil-sparing CN III palsies classically raise suspicion for aneurysmal compression, this case illustrates that microvascular ischemia particularly in patients with hypertension and hyperlipidemia can mimic this presentation. Improvement over time helps distinguish ischemic from compressive etiologies Initial concern for aneurysmal compression was raised due to non pupil-sparing CN III palsy. However, gradual improvement in EOM function and levator palpebrae,  resolution of mydriasis during rehabilitation supported a microvascular ischemic cause, which aligned with the patient’s vascular risk profile of hypertension, hyperlipidemia, PVD, and tobacco use.

Conclusions:

In elderly patients with vascular risk factors, CN III palsy with pupillary involvement does not always imply aneurysm. This case underscores the importance of thorough  evaluation, imaging, and risk stratification in guiding diagnosis of midbrain syndromes. Establishing an accurate diagnosis allows for more targeted management and can improve outcomes in Nothnagel syndrome.