[Oromandibular dystonia and botulinum toxins]

The authors describe the Meige's Syndrome also known as blepharospasm or mandibulo-oral dystonia. This Syndrome rather known by Neurologists and Ophthalmologists than by Stomatologists actually benefits by a specific treatment based on botulin toxins.

Acquired blepharoptosis

A review is given of the aetiology and possible treatment of acquired (non-congenital), blepharoptosis, which is a common but not specific sign of neurological disease. The diagnostic categories of upper eyelid drooping are scheduled as (a) pseudo-ptosis due to a local process or overactivity of eye closure, including blepharospasm, and (b) true ptosis due to a paresis of the eyelid levators (m. tarsalis superior or m. levator palpebrae) or to a disinsertion of the m. levator palpebrae (aponeurotic ptosis). A paresis of the m. tarsalis is due to a lesion in the central, intermediate or peripheral neuron of the sympathetic chain and constitutes one of the components of Horner's syndrome. A paresis of the m. levator palpebrae may be due to a failure in central innervation, in oculomotor (n.III) function, in neuromuscular transmission or to a lesion in the muscle itself.

Blepharospasm and related facial movement disorders

The variable clinical features and the relatively good response of blepharospasm to botulinum-toxin type A are now well established. The etiology and pathophysiology of blepharospasm and related facial movement disorders are still poorly understood. Genetic and histopathologic studies over the last year have contributed to our understanding of this disease. The most significant progress has been made in the electromyographic studies of the the levator palpebrae and orbicularis oculi muscles. Subclassification based on the electromyographic abnormalities of these two muscles have begun to improve our understanding of the variable responses to botulinum-toxin type A. Further electromyographic studies may help identify the best sites of injection for optimal response and differentiate patients requiring limited or complete myectomy. The development of the limited myectomy has provided excellent functional and cosmetic results with quick recovery times in selected patients.

[Dystonia as the cause of pharyngolaryngeal motility disorders]

Dystonia as cause of pharyngo-laryngeal motility disorders has not been adequately considered in most clinical ENT practices. This case study of a patient with spasmodic torticollis, Meige's syndrome and pharyngo-laryngeal motility disorder was found to be due to dystonia as the underlying cause. The possibility of local symptomatic therapy with botulinum toxin injections has currently provided the physician with an effective means for alleviating the disorder.

The interaction of the somatosensory evoked potentials to simultaneous finger stimuli in the human central nervous system. A study using direct recordings

In order to investigate the interaction of sensory electrophysiologic fields arising from the adjacent second (II) and third (III) fingers and the distant second and fifth (V) fingers, direct recordings of somatosensory evoked potentials (SEPs) were performed from the sensory and motor cortices, the sensory thalamic nucleus (nucleus ventralis caudalis, VC) and the cuneate nucleus in humans during neurosurgical operations. Electrical stimulation was given to the II, III or V fingers individually, and also to pairs of either the II and III fingers or the II and V fingers simultaneously. The interaction ratio (IR) was devised as the ratio of amplitude attenuation caused by the simultaneous stimulation to two fingers compared with the amplitude of the arithmetically summed SEPs to the individual stimulation of two fingers. The IRs were calculated on N20 and P25 from the sensory cortex, P22 from the motor cortex, P17thal from the VC, and N16cune and P35cune from the cuneate nucleus. With both stimulations to the II and III fingers and the II and V fingers, P25 showed the greatest IR, followed by P22, then by P17thal, with N16cune exhibited the smallest IR. N20 and P35cune showed similar IRs and significantly greater IRs with II and III finger stimulation compared with II and V finger stimulation. These results thus indicate that the interaction of somatosensory impulses occurs in several structures along the sensory pathway in CNS, including the cuneate nucleus, the sensory thalamic nucleus, as well as sensory and motor cortices, with the greatest IRs in the cerebral cortices and the weakest ones in the brain-stem.(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical features and factors related to the functional prognosis in Meige's syndrome]

To clarify the factors determining the amelioration of Meige's syndrome, changes of involuntary movements (IVMs) and functional disability, we examined 60 patients with Meige's syndrome during 5 years after the onset. On average, they showed gradual worsening of IVMs for approximately 2.1 years, then the IVMs ameliorated slowly. In many patients, blepharospasm appeared as the first symptom. Subsequent IVMs were seen in vicinity of the muscles of orbicularis oculi. Phasic involuntary contractions changed to tonic ones in some patients. Asynchrony of the IVMs in various facial or neck muscles may be originated from extensive pathological changes and high excitability in the brainstem. The factors determining the amelioration of functional disability are: (1) younger onset, (2) shorter duration from the onset to the period showing the worst symptoms, (3) mild IVMs when the symptoms were the worst, (4) shorter duration from the onset to the beginning of therapy, (5) synchrony of the IVMs between the muscles of orbicularis oculi and other muscles. Methylphenidate, trihexyphenidyl, and ceruletide showed a higher efficiency for IVMs than the other drugs. The drug therapy in Meige's syndrome should be started as early as possible.

Blink reflex and the masseter inhibitory reflex in patients with dystonia

The excitatory and inhibitory interneuronal pathways in the brainstem are tested by examining the blink reflex and the masseter inhibitory reflex, respectively. We studied the R2 component of the blink reflex and the SP2 component of the masseter inhibitory reflex and their recovery cycle in 56 patients with various forms of dystonia. In patients with cranial, cervical, and generalized dystonia, but not in patients with extracranial segmental dystonia, the recovery cycle of both reflexes was enhanced. The recovery cycle of R2 and SP2 can demonstrate subclinical changes in excitability of brainstem interneurons. The degree of enhancement of the recovery cycles did not correlate, however, with the severity of clinical facial muscle impairment. In addition, the recovery cycles correlated positively with each other, showing that excitatory as well as inhibitory interneuronal pathways in the brainstem are perturbed in dystonia. Study of the trigemino-facial and trigemino-trigeminal reflexes provides an objective tool for assessing functional abnormalities in dystonia.

Sensory symptoms in cranial dystonia: a potential role in the etiology?

Cranial dystonia is normally considered as a pure movement disorder. Sensory symptoms have not received much attention, but we found ill-defined pain, discomfort, distortion of sensory modalities, 'phantom' kinetic or postural sensations in the orofacial areas subsequently involved by the dyskinesia in all of 11 consecutive patients, preceding by weeks or months the motor syndrome. Physicians were often mislead, initially making diagnoses such as trigeminal neuralgia, dental problems, sicca syndrome, chronic conjunctivitis, glossitis or stomatitis. The patients reported that the orofacial movements were at first willingly performed in order to decrease the discomfort which was felt in these facial areas before the movements finally escaped voluntary control and became socially disturbing. We suspect that the sensory symptoms, for which no objective substrate could be found, and which were always reported before and in the exact location of the subsequent dyskinesia, could be the earliest manifestation of an evolving process in cranial and perhaps other focal dystonias.

Time course of distant effects of local injections of botulinum toxin

Botulinum toxin A (btx) is used to treat focal dystonias. From accidental intoxications it is known that btx can cause generalized pathologic single-fiber electromyography (SFEMG) findings. We monitored the onset and course of these disturbances in eight patients who received a small dose of btx (2-22 ng) for therapy of focal dystonias in the head/neck region for the first time via repeated SFEMG investigations at days 0, 3, 6, 9, 12, 28, and 56. Recordings were performed in the extensor digitorum brevis muscle, and in two patients additionally in the tibialis anterior muscle. In six of these patients we found an increase of jitter and blocking. The onset of these changes was in the range of 3-13 days after injection. Fiber density showed a tendency to increase. There was no correlation between SFEMG findings and the dose of injected btx. Possible mechanisms for these observations may be either a very efficient local uptake and retrograde axonal transport via the spinal motor neurons or a systemic distribution via the blood circulation.

Electrophysiological study on jaw-opening reflex recorded from digastric muscle in Parkinson's disease and primary cranial dystonias

We investigated digastric reflex excitability in normals and in patients with extrapyramidal disorders such as primary cranial dystonias and Parkinson's disease. Relationships between exteroceptive suppression of masseter muscle and digastric reflex were also investigated in some cases. Digastric reflex hyperexcitability was observed in dystonic patients when compared to normals and parkinsonian patients. Furthermore, some patients with cranial dystonia presented absence of exteroceptive suppression reflex in masseter muscle with enlarged digastric response. These results indicate hyperexcitability of the digastric reflex and abnormal agonist-antagonist muscle co-contraction in chewing reflexes of patients with cranial dystonias. This shows that digastric reflex is an important electrophysiological investigation to explore the physiopathological mechanisms of primary cranial dystonias.

Surface electromyographic study of idiopathic cranial dystonia focused on the orbicularis oculi muscles

We studied 115 Japanese patients with idiopathic cranial dystonia (Meige disease), using surface electromyography (EMG) focused on the orbicularis oculi muscles to classify the findings of the abnormal involuntary movements of this disease and to evaluate the pathophysiology of blepharospasm (BS). Surface EMGs at rest and at voluntary eyelid opening after eyelid closing were investigated. We found 62 (53.9%) patients exhibiting the overblinking type, 37 (32.2%) the tonic BS type, and 16 (13.9%) the normal type of behavior, considering the frequency of spontaneous blinking and presence of spasms. The present results suggest that BS is not a summation of blinking but a spatial and temporal extension of the orbicularis oculi muscle activity engaging in blinking, and the classification of the present study can support the investigation of the temporal characteristics of patients with this disease.

Sleep and cranial dystonia

A nocturnal polygraphic study was performed on 10 patients with cranial dystonia (blepharospasm (BS) and oromandibular dystonia (OMD)). All patients showed impaired sleep efficiency and reduced slow and REM sleep, more marked in subjects with severe dystonia. Abnormal muscular activity decreased progressively with deeper sleep and during the first hours of the night, without disappearing. A disordered hypnic++ pattern and impaired motor control even during sleep are typical features in cranial dystonia.

Neurophysiological observations on the effects of botulinum toxin treatment in patients with dystonic blepharospasm

Botulinum toxin treatment improves dystonic blepharospasm by inducing transient paresis of the orbicularis oculi muscle. It is not known if it also reduces the enhanced brainstem neuronal excitability found in this disorder. We have performed conventional electromyography (EMG) and blink reflex excitability studies on fifteen patients with blepharospasm before and after botulinum toxin treatment. Denervation signs were found with needle EMG in all treated muscles. Amplitude of the facial compound muscle action potential (CMAP) and R1 response was reduced after botulinum toxin injections. In blink reflex excitability studies, the recovery of R2 response was enhanced after treatment even when patients were tested at the time of maximal benefit from botulinum toxin injections. The results suggest that there is little influence of botulinum toxin treatment upon the enhanced excitability of brainstem interneurons in patients with blepharospasm.

[Modification of the blink reflex in hemidystonia]

With the aim of evaluating the excitability of the brain stem reflex centers, we studied the side-to-side differences in the EMG activity of the early and late components of the blink reflex, in subjects with unilateral dystonia without demonstrable brain lesions. We observed that both early and late responses of direct blink reflex were significantly higher in the affected side than in the contralateral one.

The effect of nocturnal physiological sleep on various movement disorders

Thirty-one subjects affected by different movement disorders underwent polygraphic and videotape monitoring during nocturnal sleep, to assess movement patterns during the night. It was possible to distinguish two categories of disorders according to their pattern of movements. In the largest group (Meige's syndrome, blepharospasm, amyotrophic choreoacanthocytosis, Tourette syndrome, tonic foot, hemiballism) abnormal movements were still present during sleep, but decreased in frequency and amplitude in all stages. The second group presented three syndromes (nocturnal paroxysmal dystonia, nocturnal myoclonus, restless legs syndrome), in which light non-rapid-eye-movement sleep induced a strong activation of abnormal movements, whereas rapid-eye-movement sleep suppressed them.

Diurnal variability in cranial dystonia

Eleven patients with cranial dystonia were investigated for diurnal variations in disability by means of video recordings. Disability increased significantly from morning to evening. The increase was not related to changes in vigilance levels assessed by dynamic electroencephalogram. Cranial movement disorders display diurnal fluctuations that are probably related to endogenous circadian rhythms.

Facial dystonia: clinical features, prognosis and pharmacology in 31 patients

The natural history and response to different treatments were assessed in 31 consecutive patients with blepharospasm (BS) and/or oromandibular dystonia (OMD). The mean age at onset was 52.4 years and there was a female preponderance of 2.5 to 1. Ocular symptoms preceded the onset of blepharospasm in more than 50% of the affected patients, whereas psychiatric and dental problems prior to the onset of focal dystonia were found in 10% and 13% of the cases respectively. Dystonia elsewhere, mainly in the craniocervical area, was found in 23% of patients and appeared to follow a somatotopic progression. The first 2-3 years of history were crucial for the spread of dystonia to other face and body parts. When OMD was the first symptom, a lower tendency of dystonia to progress elsewhere was observed. A putative cause was found in 14% of patients who showed clinical and radiographic evidence of basal ganglia or rostral brainstem-diencephalon lesions. The response to different drugs was inconsistent although transient improvement was induced by haloperidol in 6 patients, by L-Dopa plus deprenyl in 3 patients, by trihexyphenidyl in 2 patients and by clonazepam in 2 patients. One, apparently spontaneous, remission was observed. Botulinum A toxin was injected in the orbicularis oculi of 8 patients affected by BS: moderate to marked improvement lasting 5 to 30 weeks (mean 14.5 weeks) was achieved in all cases; transient ptosis, lasting 1 to 3 weeks, occurred in 3 cases.

Effects of anticholinergic agents on the excitability of the blink reflex in Meige syndrome

Blink reflex recovery cycle, before and after acute administration of orphenadrine chlorhydrate, was tested in Meige syndrome. Data here reported show, after the drug, a decrease of the unconditioned polysynaptic responses, without a significant modification of the blink reflex recovery curves. This fact rules out a specific effect of anticholinergic drugs on the pathological reduction of the inhibitory process, at an interneuronal level of these polysynaptic pathways, in Meige syndrome.

Meige syndrome: an unusual cause of involuntary facial movements

Dental and allied health professionals are on occasion confronted with patients who exhibit abnormal facial movements. These patients may be seeking a diagnosis or may relate a specific problem resulting from the uncontrolled and involuntary orofacial movements. A complete description of the various conditions associated with abnormal facial movements is beyond the scope of this article. Instead, these authors present a case with dental symptoms that were masking a more serious underlying progressive neurologic disorder. Appropriate referral to the neurology service is essential so that treatment of the underlying cause may precede, rather than follow, empiric management of these patients' symptoms.

Meige syndrome: neuropathology of a case

Primary Meige syndrome is a form of cranial dystonia of unknown cause. Only three postmortem studies have been reported, and the results of these studies have not been consistent. We have examined the brain of a 72-year-old man with typical primary Meige syndrome and found mild to moderate cell loss in the zona compacta of the substantia nigra, locus ceruleus, midbrain tectum, and dentate nucleus of the cerebellum. Also frequent Lewy bodies were present in pigmented nuclei of the brainstem. No abnormalities were detected elsewhere. These pathological findings support the notion that brainstem pathology is important in the pathophysiology of cranial dystonia.

Coexistent Meige's syndrome and myasthenia gravis. A relationship between blinking and extraocular muscle fatigue?

We studied five patients with a combination of Meige's syndrome (blepharospasm-oromandibular dystonia) and myasthenia gravis. The coexistence of two disorders impairing eyelid opening led to diagnostic confusion and delayed appropriate therapy. Detailed oculographic monitoring of one patient indicated that eye position drifting due to myasthenic oculomotor fatigue was corrected by eye blinks, and that blinks tended to occur with slower saccades. Our observations suggest that fatigue of extraocular muscles may lead to synkinetic blinking and perhaps eventually to autonomous blepharospasm.

Pathophysiology of blepharospasm and oromandibular dystonia

The pathophysiology of reflexes mediated by the fifth and seventh cranial nerves has been studied in 16 patients with blepharospasm and oromandibular dystonia compared with normal age-matched subjects. The EMG activity of the dystonic spasms in the periocular and jaw muscles was similar to that described in other muscles in patients with generalized torsion dystonia. The latency of the R1 and R2 components of the blink reflex and of the corneal reflex was normal. However, the amplitude and the duration of the R1 and R2 and the duration of the corneal reflex were increased. In some patients the R1 component was also present on the side contralateral to the stimulus, while in normal subjects it was present only on the ipsilateral side. The excitability cycle of recovery of the R2 component of the blink reflex after a prior conditioning shock was enhanced in the patients. There were no EEG potentials preceding blepharospasms in the patients, although a Bereitschaftspotential was seen beginning some 500 ms prior to voluntary blinks in the same individuals. Exteroceptive suppression in the contracting masseter and orbicularis oculi muscles was absent in 40 to 50 per cent of the patients. The jaw jerk was present in all the patients with normal latency. These results indicate that the neuronal arcs of the facial reflexes in blepharospasm and oromandibular dystonia are normal. However, there is an abnormal excitatory drive, perhaps from the basal ganglia, to the facial motoneurons and the interneurons which mediate the facial reflexes in the brainstem.

"Trick" movements in facial dystonia

Two patients with facial dystonia (blepharospasm and/or oromandibular dystonia) presented with an unusual "trick" movement. Both patients were able to inhibit blepharospasm and oromandibular dystonia by vocalizations including singing, reading, and speaking spontaneously. The significance of "trick" movements in facial dystonia is discussed.