1015 - Post-Traumatic Parkinsonism and Serotonin Syndrome Following Severe Traumatic Brain Injury: A Case Report

Thursday, February 19, 2026

5:00 PM - 6:30 PM AST

Presenting Author(s)

CM

Christopher McLeod, MPH

Medical Student
UT Southwestern Medical Center
Dallas, Texas, United States
DA

Dustin Averitt, DO

Resident Physician
Dell Medical School at the University of Texas at Austin
Austin, Texas, United States

Co-Author(s)

KW

Kristin Wong, MD

Associate Professor
University of Texas at Austin, Dell Medical School
Austin, Texas, United States

Submitter(s)

DA

Dustin Averitt, DO

Dell Medical School at the University of Texas at Austin
Austin, Texas, United States

Case Diagnosis: Concurrent post-traumatic parkinsonism (PTP) and serotonin syndrome in the setting of basal ganglia injury and polypharmacy.

Case Description: A 31-year-old man with no medical history presented to a level I trauma hospital after jumping from a moving vehicle at high speed. Imaging revealed bilateral hemorrhagic contusions, subdural hematomas, and left cerebellar parenchymal hemorrhage. He required intubation and was admitted to the surgical intensive care unit. PM&R was consulted on hospital day 22. The patient was fully oriented but exhibited lethargy, tachycardia, diaphoresis, masked facies, bradykinesia, hypophonia, clonus, right upper extremity tremor, spasticity and rigidity in all extremities. He was receiving trazodone, quetiapine, and haloperidol for agitation. Concern for serotonin syndrome led to discontinuation of these medications, after which autonomic instability resolved. EEG for persistent tremor was negative for seizure. MRI demonstrated axonal shear injury of the midbrain and bilateral basal ganglia. A carbidopa/levodopa trial resulted in improved parkinsonian features including tremor, bradykinesia, hypophonia, masked facies, and rigidity. His functional status improved, and he discharged to IPR.

Discussions: PTP arises from disruption of the nigrostriatal dopaminergic pathway, frequently due to basal ganglia or midbrain injury. Damage to these areas also increases susceptibility to serotonin syndrome. This patient displayed signs and symptoms of concurrent serotonin syndrome and PTP. Serotonergic agents likely triggered serotonin syndrome per Hunter criteria, while dopamine antagonists worsened PTP symptoms. Overlapping manifestations of serotonin syndrome, PTP, and severe traumatic brain injury (TBI) complicated diagnosis and management. This case highlights the diagnostic complexity of neurotransmitter dysregulation disorders following TBI.

Conclusions: Patients with TBI, particularly involving basal ganglia injury, are at elevated risk for both serotonin syndrome and parkinsonism. Serotonergic and antidopaminergic medications should be used cautiously, and delayed recognition of adverse drug effects are detrimental. Distinguishing between structural post-traumatic movement disorders and iatrogenic syndromes following TBI is critical for optimal recovery.