Dear Editor,
Meige syndrome [
1] is an adult-onset craniofacial dystonia characterized by the combination of blepharospasm and oromandibular dystonia [
2]. It can be a primary (idiopathic) or parkinsonian condition [
2]. Among the symptomatic therapies, the peripheral application of botulinum toxins (BTXs) is currently considered the most effective treatment for Meige syndrome [
2], but its therapeutic efficacy varies and is not long-lasting. In clinical practice, treating Meige syndrome with conventional therapeutic tools is often difficult. It has been hypothesized that imbalanced activities between dopamine D
1- and D
2-type receptors (D
1Rs and D
2Rs) in the striatum might cause repetitive stereotyped motor symptoms, which are the key features of dystonia [
3-
5]. Here, we report the striking and long-lasting benefits of dual dopaminergic modulation (DDM) via the use of L-DOPA and chlorpromazine (CPZ) [
4,
5] in a patient with idiopathic Meige syndrome who poorly responded to BTX treatment.
A 73-year-old woman experienced gradual onset and worsening of blepharospasm and oromandibular dystonia beginning at age 67. She had no prior exposure to neuroleptics and no family history of dystonia. She had no history of alcohol consumption or smoking. Upon admission, she exhibited marked facial grimacing with excessive blinking or sustained forceful eye closure in combination with forced contractions of the jaw and tongue muscles, leading to difficulty in opening the mouse to speak and eat. Severe spasmodic dysphonia was also observed. All dystonia symptoms were sustained throughout the day and were exacerbated by emotional and physical stresses. Physical examinations revealed no cranial nerve abnormalities or overt parkinsonism. Brain MRI showed no obvious abnormalities. Laboratory testing revealed no abnormalities, and no pathogenic variants in the known dystonia genes were identified by whole-exome sequencing (OMIM Phenotypic Series PS128100;
https://omim.org/phenotypicSeries/PS128100). Thus, she was diagnosed with idiopathic Meige syndrome.
Oral medication with lorazepam, etizolam, loflazepate, or paroxetine was not beneficial. She refused to take anticholinergics because of possible cognitive decline. Accordingly, she received a total of 100 units of BotoxTM, which was injected bilaterally into the orbicularis oculi (25 units), orbicularis oris (20 units), corrugator (5 units), masseter (10 units), and platysma (40 units) muscles. However, this BTX treatment did not achieve any satisfactory results at the 3-month follow-up.
She then underwent DDM using L-DOPA and CPZ. Before the treatment, her Burke-Fahn-Marsden Dystonia Movement Scale (BFMDMS) [
6] and Dystonia Disability Scale (BFMDDS) [
6] scores were 20 (maximum 120) and 10 (maximum 30), respectively. As shown in
Figure 1A, daily doses of L-DOPA/carbidopa and CPZ-phenolphthalinate were increased stepwise up to 150 mg/day and 15 mg/day, respectively, over 8 weeks [
4,
5]. Clinical evaluation and video recording were performed 1 day before (baseline) and 2, 4, and 8 weeks after drug initiation. As a result, DDM using L-DOPA and CPZ attenuated her dystonia symptoms in a dose-related manner (
Figure 1B, Supplementary Video 1 in the online-only Data Supplement). When L-DOPA/carbidopa (150 mg/day) and CPZ-phenolphthalinate (15 mg/day) were used, her blepharospasm and oromandibular dystonia were almost completely resolved (Supplementary Video 1 in the online-only Data Supplement). Complete remission of spasmodic dysphonia was also observed. Her BFMDMS and BFMDDS scores were 1 and 1, respectively (
Figure 1B). This striking benefit obtained with DDM using DOPA/carbidopa (150 mg/day) and CPZ-phenolphthalinate (15 mg/day) remains unchanged at the time of this writing, which is more than one year after treatment. No adverse effects have been observed thus far.
In our patient with idiopathic Meige syndrome, all aspects of dystonia symptoms could be markedly alleviated by DDM using L-DOPA and CPZ (L-DOPA/CPZ) at doses lower than those used in the clinic. Since L-DOPA is a D1/D2 agonist and CPZ is a D2 antagonist, her dystonia symptoms might be alleviated through DDM, which induces an increase in D1 signaling with a relative decrease in D2 signaling in the striatum.
The key features of dystonia are characterized by repetitive and stereotyped motor symptoms [
3-
5]. It is hypothesized that repetitive stereotyped motor and cognitive symptoms might be due to the altered function of a neural circuit connecting the prefrontal cortex with the striatal “striosomes”, which participate in reinforcement-related learning and decision-making under conflict [
7]. This hypothesis implies that the output activity of the cortico-striatal (striosomal) network, which receives afferent signals through the monosynaptic and/or multisynaptic pathways arising from various brain regions, such as the thalamus, cerebellum, and brainstem, is important in considering dystonia pathology and treatment. Corticostriatal inputs are largely integrated by striatal medium spiny neurons (MSNs), which constitute the vast majority of striatal neurons and constitute the major striatal efferent system in basal ganglia circuits [
7].
Deregulation of striatal dopamine signaling is a potential cause of dystonia [
4,
5]. The loss of dopamine D
1 signaling in striatal striosomes has been proposed to be an important pathology that induces dystonia [
3-
5]. A modular computational model of the basal ganglia circuits suggested that striosomal D
1 signaling participates in the representation of motor action selection (or focusing) and that its impairments cause stereotyped motor symptoms [
3]. This assumption is relevant to the functional pathology of several human disease models of dystonia, such as DYT25 and DYT3 (X-linked dystonia-parkinsonism) [
4]. It is thus conceivable that striosomal loss of D
1 signaling underlies the dystonia manifestation in Meige syndrome patients.
The specificity of the striatal dopamine D
1 system in humans [
8] is the neural basis for the therapeutic mechanism of DDM using low doses of L-DOPA/CPZ for the treatment of idiopathic dystonia [
4,
5]. The human neostriatum exhibits a pronounced enrichment of D
1Rs in the striosomal MSNs but a relative paucity of D
1Rs in the matrix MSNs [
8]. These findings suggest that a low dose of L-DOPA could exert its D
1-agonistic effects primarily on striosomal MSNs. We thus believe that DDM using low doses of L-DOPA/CPZ could improve dystonia symptoms by increasing striosomal D
1-activity [
4,
5]. Moreover, the concurrent use of CPZ may strengthen the D
1-agonistic effect of L-DOPA on the striosomal network in a synergistic manner [
4,
5].
In conclusion, DDM using low doses of L-DOPA/CPZ could exert a striking and long-lasting therapeutic effect on patients with idiopathic Meige syndrome refractory to BTX treatment. Since DDM therapy has also been effective for idiopathic blepharospasm [
4] and cervical dystonia [
5], further investigations of this treatment modality for a wide spectrum of idiopathic dystonia, including Meige syndrome, may be warranted.