Objective: To contribute to the better understanding of blepharospasm, we systematically assess olfactory and gustatory ability in subjects with blepharospasm, compared to subjects with cervical dystonia and healthy controls.

Background: Blepharospasm is characterized by spasms of eyelid muscles. It is considered a form of focal dystonia together with conditions such as cervical dystonia. The pathophysiology of the focal dystonia is not completely understood. Current concepts propose alterations of a network including basal ganglia, sensorimotor cortex, cerebellum and thalamus. While this network is primarily concerned with sensorimotor control, several lines of evidence suggest that these structures are also involved in the chemical senses. Diminished olfactory and gustatory functioning in subjects with cervical dystonia also point into this direction (PMID 29724603; 32062706).  Based on the overlap between neuroanatomical regions involved in the pathophysiology of blepharospasm and processing of information related to the chemical senses, altered sense of smell and taste may be found in blepharospasm. Botulinum toxin is an established treatment for blepharospasm, but effects on the chemical sense have not been systematically assessed.

Method: 19 subjects with idiopathic blepharospasm (age 66,58 ± 8,7 years, 14 female / 5 male), 40 subjects with cervical dystonia (age 61.8 ± 10.9 years, 23 female / 17 male) and 55 healthy controls (age 63.3 ± 10.8 years, 32 female / 23 male) were assessed. The Sniffin Sticks to assess odor threshold, discrimination and identification as well as the Taste Strips to assess the combined taste score were applied. 10 subjects with blepharospasm were assessed before and 1 month after botulinum toxin treatment. For comparison, 10 healthy controls were also assessed twice 1 month apart. Findings were compared by t-test.

Results: Subjects with blepharospasm had lower odor threshold scores than healthy controls, while subjects with cervical dystonia had lower odor threshold, in addition to diminished odor discrimination and taste score as compared to healthy controls. Treatment with botulinum toxin did not affect the chemical senses in subjects with blepharospasm.

Conclusion: Blepharospasm may be related to subtle impairments of the sense of smell. Findings contribute to the understanding of the non-motor spectrum of blepharospasm. Botulinum toxin is a safe treatment for blepharospasm and dose not impact the chemical senses.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/smell-and-taste-in-blepharospasm/