Is increased blinking a form of blepharospasm?

Abstract

Objective: The aim of this study was to investigate whether increased blink rate (BR) is part of the clinical spectrum of primary blepharospasm (BSP). Methods:We enrolled 40 patients (16 patients with an increased BR but without typical orbicularis oculi [OO] spasms, and 24 patients with typical involuntary OO spasms) and 18 healthy subjects. The BR, blink reflex recovery cycle, and somatosensory temporal discrimination threshold (STDT) were tested in patients and controls.Results: Patients who had typical OO spasms had an altered R2 recovery cycle whereas those who had an increased BR alone had a normal blink reflex recovery cycle. STDT values were higher in patients than in healthy subjects and no difference was found in the STDT abnormalities in the 2 groups of patients.Conclusions: Our study shows that, despite the similar STDT abnormalities, the different changes in the R2 recovery cycle in patients with BSP and those with increased BR alone suggest that these disorders arise from different pathologic mechanisms. Neurology Patients who present with excessive involuntary eyelid closure raise a diagnostic challenge. Whereas some patients have sustained orbicularis oculi (OO) spasms and are therefore diagnosed as having blepharospasm (BSP), a common focal dystonia, 1-4 others have increased blinking alone. In these patients, increased blinking may reflect ophthalmologic disorders involving the ocular surface, tear film, or eyelids but can manifest also in apparently healthy subjects without any secondary causes.5 Although increased blinking at rest and during conversation may occur in patients with BSP, 6 and some suggest that increased blinking is sometimes a prodromal sign of primary BSP, 2 no evidence yet shows whether patients with increased blinking alone have a dystonia subtype, essentially a forme fruste of BSP.Our aim in this case-control study was to investigate whether increased blinking is a subtype of primary BSP. To do so, we tested the blink rate (BR) and the neurophysiologic variables known to be altered in primary BSP, the blink reflex recovery cycle-reflecting brainstem excitability [7][8][9][10] -and somatosensory temporal discrimination threshold (STDT), [11][12][13] in patients presenting with excessive involuntary eyelid closure who had sustained OO spasms (primary BSP), those with increased blinking alone, and healthy age-matched control subjects.METHODS Study participants. Among consecutive patients with excessive involuntary eyelid closure who were seen in our movement disorders outpatient clinic, we identified 16 subjects with increased blinking without sustained OO spasms. These subjects could not voluntarily control the excessive blinking and reported no premonitory sensation before eyelid movements. Nor did any evidence suggest a psychogenic movement disorder such as persisting unilateral or asymmetric symptoms, paroxysmal symptoms, and other inconsistencies such as pain, associated somatizations, blinking diminished by distraction, unusual sensory tricks, or unexpected res...

Blepharospasm 40 years later

“…Bentivoglio and colleagues demonstrated that the blink rate at rest and during conversation was higher in patients with blepharospasm than in healthy controls. The finding of an increased blink rate at rest was confirmed by Conte and colleagues . Increased blinking may precede the appearance of OO spasms, thus representing a forme fruste of blepharospasm.…”

Botulinum toxin and blink rate in patients with blepharospasm and increased blinking

“…Whether patients with OO spasms have a different pathophysiology from patients showing only IB is still unclear. In a recent study8 we observed that, differently from patients with BSP, patients with IB do not have an enhanced recovery cycle of blink reflex circuits. Patients with BSP and those with IB, however, share similar abnormalities in somatosensory temporal discrimination threshold (STDT).…”

“…It is also known that there is a direct relation between lacrimal drainage capacity and BR 41. In patients with IB and in those BSP with increased BR and hyperexcitability of the spontaneous blink circuit, there may be increased tear film turnover, thereby causing a ‘relative dryness’ of the ocular surface 8. This mechanism may therefore promote the overactivation of the spontaneous blink generator.…”

“…Patients with BSP and those with IB, however, share similar abnormalities in somatosensory temporal discrimination threshold (STDT). Although STDT abnormalities are also present in pathological conditions other than dystonia,9–12 the similar abnormalities in STDT values in IB and BSP patient groups may well be a feature indicating continuity from IB to spasm 8…”

“…Several clinical features are often associated with OO spasms, including an increased spontaneous blink rate (BR) and sensory symptoms in the eyes 5 6. Since an increased BR may precede the development of the condition, BSP patients may also display increased blinking (IB) in the absence of spasms of the OO muscles 7 8. Whether patients with OO spasms have a different pathophysiology from patients showing only IB is still unclear.…”