Abstract
Purpose
The objective of this clinical study was to investigate the history and clinical findings in 10 patients having an essential palatal tremor. Furthermore, a botulinum toxin A (BTA) therapy in 5 cases was carried out, and the outcome was analyzed.
Materials and Methods
Seven adult and 3 pediatric patients with essential palatal tremor were examined at presentation, before and after start of treatment, and every 3 months or when symptoms recurred. Findings were documented by endoscopic video recordings, electromyography, tympanometry, and ear canal microphone recording. The BTA injections were performed in local or general anesthesia, under elecromyographic guidance.
Results
The BTA therapy in all 5 patients was successful. Surprisingly, 2 of these patients, aged 10 and 6 years, remained in remission for several years after a single successful injection.
Conclusion
Botulinum toxin therapy is a safe and effective treatment of essential palatal tremor and seems to be especially useful in pediatric patients. The long lasting effect in children hints toward a pathophysiologic difference between pediatric and adult essential palatal tremor.
1
Introduction
Essential palatal tremor (EPT), also called essential palatal myoclonus , is a rare disease in adults and children. It consists of unvolountary repetitive contractions of the soft palate with involvement of musculus tensor veli palatini, musculus levator veli palatini, and in some cases other oropharyngeal muscles. The contractions of musculus tensor veli palatini cause a short-term unilateral or bilateral opening of the eustachian tube. The main symptom is an objective clicking tinnitus that can seriously debilitate the patient and is audible to the examiner, sometimes more than a distance of several meters . The mode of generation of this clicking sound is not definitely elucidated. Potentially, the noise is produced by the walls of the eustachian tube snapping together , or possibly, the separation of the tube walls with breaking of surface tension generates it . Even an acoustic impedance study of peritubal myoclonus could not distinguish between these 2 mechanisms . However, it is also conceivable that the clicks are caused by contraction of the musculus tensor veli palatini itself.
Essential palatal tremor has already been described 140 years ago . Since then, predominantly case reports on this condition have been published. By reviewing the literature on 287 patients with palatal tremor, Deuschl et al could define EPT as a self-standing entity and demarcate it from symptomatic palatal tremor (SPT), using clinical and pathologic features. Symptomatic palatal tremor is characterized by a lesion of the connections between nucleus dentatus, nucleus ruber, and the inferior olivary complex (also known as the Guillain-Mollaret triangle ). It generally develops secondary to brainstem or cerebellar disease. Etiology and pathogenesis of SPT is rather well understood. Contrarily, in EPT, a dysfunction without morphological changes is assumed. Additional neurologic deficits are lacking in EPT. To date, there is little knowledge available on etiology and pathogenesis .
2
Materials and methods
Between 2004 and 2008, 10 patients were diagnosed with EPT at our institution. All of them reported a persistent clicking tinnitus, which could be heard externally by the examiner. Patients were interviewed in detail about onset, characteristics of the tinnitus, and accompanying symptoms and were physically examined. Besides the general otorhinolaryngological and neurologic examinations, we performed otomicroscopy, nasal endoscopy, pure tone and speech audiometry, and video documentaion of the palatal tremor. Furthermore, a cranial and brainstem magnetic resonance imaging (MRI) to rule out morphological changes was performed. Only patients with EPT were included in our study, that is, patients without pathologic findings on MRI and without other intrinsic neurologic pathologic findings. To characterize the objective clicking tinnitus, we recorded the EPT with an ear canal microphone and with a continuous tympanometry, determining the frequency of the clicks ( Fig. 1 ).
The patients were informed about possible treatment options (wait and see, anticonvulsants or sedatives, surgery, botulinum toxin injection). Of the 10 patients, 5 opted for a botulinum toxin A (BTA) therapy, after detailed information on risks and possible side effects, and gave written informed consent. In case of the 2 underaged children, the decision was made together with the parents. One patient first chose treatment with carbamazepine. The remaining 4 patients initially opted for a wait-and-see regimen. When EPT persisted or worsened, an appointment for reevaluation of treatment was arranged.
Five hundred mouse units (MU) BTA (preparation Dysport; Ipsen Pharma, Ettlingen, Germany) were dissolved in 2.5 mL of sterile NaCl solution (0.9%), resulting in a concentration of 200 MU/mL, and drawn up in a tuberculin syringe. Under electromyographic guidance, a total amount of 20 to 60 MU BTA was injected into the soft palate unilaterally or bilaterally. The point of injection was the area of maximal myoclonic activity in the musculus tensor veli palatini/musculus levator veli palatini ( Fig. 2 ). The maximum dose injected into one side was 30 MU. In one patient, 10 MU of BTA purchased from the manufacturer Allergan (preparation Botox; Pharm Allergan, Ettlingen, Germany), at a concentration of 12.5 MU/mL, was used at the first treatment session. In all further treatments, the preparation Dysport was used. The botulinum neurotoxin (BoNT) injections were performed in general anesthesia in one 6-year-old boy. During the anesthesia, the EPT paused, and no myoclonic activity was recordable electromyographically. In this patient, we injected at the typical location “posteromedially to the maxillary tuberosity” . In all other patients, the injections were performed under local superficial anesthesia with tetracain spray.
The therapeutic outcome was documented with a clinical examination, audiological testing, and video recording. During the follow-up, regular telephone interviews with the patients and—if applicable—with the patients’ parents took place every 3 months. When symptoms recurred, a visit at our institution and, if necessary, a further BoNT injection followed.
2
Materials and methods
Between 2004 and 2008, 10 patients were diagnosed with EPT at our institution. All of them reported a persistent clicking tinnitus, which could be heard externally by the examiner. Patients were interviewed in detail about onset, characteristics of the tinnitus, and accompanying symptoms and were physically examined. Besides the general otorhinolaryngological and neurologic examinations, we performed otomicroscopy, nasal endoscopy, pure tone and speech audiometry, and video documentaion of the palatal tremor. Furthermore, a cranial and brainstem magnetic resonance imaging (MRI) to rule out morphological changes was performed. Only patients with EPT were included in our study, that is, patients without pathologic findings on MRI and without other intrinsic neurologic pathologic findings. To characterize the objective clicking tinnitus, we recorded the EPT with an ear canal microphone and with a continuous tympanometry, determining the frequency of the clicks ( Fig. 1 ).
The patients were informed about possible treatment options (wait and see, anticonvulsants or sedatives, surgery, botulinum toxin injection). Of the 10 patients, 5 opted for a botulinum toxin A (BTA) therapy, after detailed information on risks and possible side effects, and gave written informed consent. In case of the 2 underaged children, the decision was made together with the parents. One patient first chose treatment with carbamazepine. The remaining 4 patients initially opted for a wait-and-see regimen. When EPT persisted or worsened, an appointment for reevaluation of treatment was arranged.
Five hundred mouse units (MU) BTA (preparation Dysport; Ipsen Pharma, Ettlingen, Germany) were dissolved in 2.5 mL of sterile NaCl solution (0.9%), resulting in a concentration of 200 MU/mL, and drawn up in a tuberculin syringe. Under electromyographic guidance, a total amount of 20 to 60 MU BTA was injected into the soft palate unilaterally or bilaterally. The point of injection was the area of maximal myoclonic activity in the musculus tensor veli palatini/musculus levator veli palatini ( Fig. 2 ). The maximum dose injected into one side was 30 MU. In one patient, 10 MU of BTA purchased from the manufacturer Allergan (preparation Botox; Pharm Allergan, Ettlingen, Germany), at a concentration of 12.5 MU/mL, was used at the first treatment session. In all further treatments, the preparation Dysport was used. The botulinum neurotoxin (BoNT) injections were performed in general anesthesia in one 6-year-old boy. During the anesthesia, the EPT paused, and no myoclonic activity was recordable electromyographically. In this patient, we injected at the typical location “posteromedially to the maxillary tuberosity” . In all other patients, the injections were performed under local superficial anesthesia with tetracain spray.
The therapeutic outcome was documented with a clinical examination, audiological testing, and video recording. During the follow-up, regular telephone interviews with the patients and—if applicable—with the patients’ parents took place every 3 months. When symptoms recurred, a visit at our institution and, if necessary, a further BoNT injection followed.
3
Results
3.1
Symptoms and findings
The 10 patients with EPT were between 6 and 68 years old (mean, 36 years) at presentation. The sex distribution was 1:1. Essential palatal tremor was reported to be present since 1 to 456 months (mean, 70 months). Six patients could mention a triggering factor for the clicking tinnitus ( Table 1 ). In 4 patients, the tinnitus was present unilaterally; in 5 patients, it was asymmetrically bilateral; and in 1 patient, it was symmetrically bilateral. The measured frequency varied between 30 and 100 per minute (mean, 69/min). All patients could voluntarily suppress the EPT for some seconds by Valsalva maneuver or by contracting pharyngeal muscles. Often, the use of a tongue depressor by the examiner caused the EPT to pause. Measurements of sound pressure level with an ear canal microphone yielded maximal values of 88 dB in the 10-year-old girl.
