Diagnostic Approach to Olfactory Hallucinations

Initial Clinical Assessment

The American College of Radiology recommends determining the timing and pattern of hallucinations, as well as associated symptoms such as headache, seizure activity, psychiatric symptoms, or other neurological deficits, to guide further workup 1, 2, 3, 4, 5, 6
The presence of concurrent neurological deficits, such as facial pain, visual changes, or motor weakness, requires urgent workup 7, 8
Altered consciousness or confusion suggesting encephalitis or status epilepticus also necessitates prompt evaluation 6

The American College of Radiology suggests that MRI brain with contrast is the initial imaging modality of choice for evaluating olfactory hallucinations, covering the olfactory pathway 1, 2, 3, 4, 5
The MRI protocol should include T1-weighted, T2-weighted, FLAIR sequences, and contrast-enhanced sequences 1, 2, 3, 4, 5
Objective olfactory testing is recommended but not required for diagnosis, and can characterize the degree of olfactory function 1, 9, 10

The American College of Radiology recommends immediate neurosurgical or neuro-oncology consultation for masses such as glioblastoma multiforme, meningioma, or esthesioneuroblastoma 1
Initiate anticonvulsant therapy as first-line treatment for idiopathic olfactory hallucinations or those associated with epileptiform activity, with sodium valproate as a first-line option 8
The American Academy of Neurology and the American College of Radiology suggest considering alternative treatments, such as GABA-enhancing agents, if first-line options are ineffective 1, 2, 3, 4, 5