INTRODUCTION
DISCUSSION
REFERENCES
 

PALATAL MYOCLONUS: AN UNCOMMON ASSOCIATION WITH DYSPHAGIA, DYSARTHRIA AND SPIRATION - A CASE REPORT
Karen Chua, MBBS, MRCP, FAMS*;  Sarah Wallace, B Sc (Speech Path), RCSLT**

From the *Department of Rehabilitation Medicine, **Therapy Services, Tan Tock Seng Hospital, Singapore. Address reprint requests to: Dr Karen Chua, Department of Rehabilitation Medicine, Tan Tock Seng Hospital, 17, Ang Mo Kio Ave 9, Singapore 569766, Republic of Singapore, Fax: (65) 64590 414, Tel: (65) 64506 165, E-mail: Karen_Chua@ttsh.com.sg

Symptomatic Palatal Myoclonus (PM) is an uncommon association with dysphagia, dysarthria and aspiration. It causes involuntary and rhythmic muscular contractions of the palatal musculature. We report a case of bilateral synchronous palato-pharyngeal-larygngeal myoclonus associated with dysphagia, dysphonia, dysarthria, severe ataxia and functional impairment. The underlying cause was a brainstem stroke. Fibreoptic Endoscopic Evaluation of Swallowing (FEES) was employed to aid the clinical diagnosis and evaluate the presence of aspiration. Treatment consisted of intensive rehabilitation, medication trials and a dysphagia program enabling safe oral feeding. The pathophysiology, causes, and management of palatal myoclonus are discussed together with a review of the literature.

Key Words: Palatal Myoclonus, Brainstem Stroke, Oral Feeding

INTRODUCTION :
          Palatal myoclonus (PM) is a rare movement disorder of the soft palate characterized by rhythmic, usually bilateral, involuntary contractions of the palatal musculature occurring at a rate of 40-240 times a minute¹. It may be associated with myoclonus of distant muscle groups including the pharyngeal, ocular, facial, laryngeal and diaphragmatic muscles. First described by Politzer, PM may be associated with dysarthria, dysphagia with concomitant aspiration, irregular respiration and airway obstruction^2-5. PM may be essential (idiopathic) or secondary, related to a variety of neurological insults. The former is often associated with tinnitus, in contrast to secondary PM where tinnitus is uncommon^5,6. Essential myoclonus usually occurs in younger patients and is non-progressive, while secondary PM is often associated with lesions in the brainstem and cerebellum, such as cerebrovascular accidents, trauma, tumour, demyelinating or infective causes^4,7,8. We report a case of symptomatic palatal myoclonus caused by an underlying brainstem stroke.

Case Report
          YML, a 65-year old Chinese female presented with a 3-month history of dysphagia, severe dysphonia and dysarthria. Pertinent medical history included that of essential hypertension, which was controlled with beta-blockers. She had a history of cerebellar hemorrhage 11 months before when she presented with acute headache, vomiting and altered mental status. CT scans showed a large cerebellar haematoma with intraventricular extension into both lateral horns and fourth ventricle.
          Emergency posterior fossa craniotomy, evacuation of haematoma, and insertion of an external ventricular drain were performed. Angiograms were negative for vascular abnormalities. Post-operatively, she remained in a minimally responsive, tetraplegic and dependent state and was discharged 2 months later, to a nursing home without any community-based rehabilitation.
          3 months later, she was readmitted to hospital for aspiration pneumonia. When reassessed, her neurological and cognitive status was unchanged. CT scans of the brain did not show significant ventricular dilatation or new stroke. At 9 months post-stroke, she was again reassessed. Her level of arousal had increased, and she was able to obey simple one-step commands. Motor strength was 4/4 in the upper and lower limbs with truncal ataxia. Severe dysarthria, dysphonia, and dysphagia were present. She remained wheelchair-bound and dependent for all activities of daily living.
          She was admitted to a level II inpatient rehabilitation facility at 9 months post-stroke. Her rehabilitation programme consisted of physiatrist-directed multidisciplinary rehabilitation therapies amounting to 3 hours per day, 5 days per week, consisting of dysphagia and speech therapy, physiotherapy, and occupational therapy with rest on weekends.
          Initial clinical bedside swallowing evaluation by a speech therapist showed significant difficulties in both oral and pharyngeal phases of swallowing. Delayed initiation of swallows, drooling of food and liquids, and reduced laryngeal elevation were noted. Involuntary movements suggestive of myoclonus were observed in the orofacial muscles with inability to maintain lip closure and incoordinated tongue movements. Her voice quality was wet and harsh; and reflexive cough was absent. There was also incoordination of breathing and swallowing. Dysphonia was noted and laryngeal myoclonus was suspected. Her head control was also poor. She was assessed to have spastic-ataxic dysarthria with incoordination of respiration and phonation, reduced breath support and dysprosodic speech. All these gave rise to extremely poor speech intelligibility.
          To further evaluate her swallowing and PM, fibreoptic endoscopic evaluation of swallowing (FEES) was performed by the speech therapist within 3 days of admission to rehabilitation, using a standard ENF-P3 nasoendoscope with an Olympus CLK-4 light source and Olympus OTV-S5 camera system and video recorder. The procedure was done in the manner described by Langmore and McCulloch²⁵. FEES showed widespread bilateral synchronous myoclonus in the soft palate, pharyngeal wall constrictor muscles and involvement of all laryngeal structures including the vocal folds. Pooling of secretions in the larynx and poor laryngeal sensation was present. Delayed swallow initiation resulted in premature spillage of food and liquid into the valleculae and piriform sinuses. Aspiration occurred on honey consistency and thin liquids. Her cough response was ineffective in clearing aspirated material from the trachea.
          Intensive dysphagia therapy was commenced with close supervision of a modified consistency diet (blended diet and thickened fluids to honey consistency) together with specific swallowing strategies (use of chin tuck head position and multiple swallows) to limit the amount of laryngeal penetration. Her nasogastric tube was removed 11 days after admission to rehabilitation and she was able to maintain stable nutritional status. She was subsequently upgraded to a soft diet with thickened fluids (nectar consistency) one month later and could feed herself with moderate assistance. No episodes of aspiration pneumonia were documented during rehabilitation.
          Compensatory strategies were used to improve breath support and improve intelligibility Ð diaphragmatic breathing, preceding speech with a purposeful breath and limiting herself to short phrases. This resulted in appreciable improvements in her voice quality and intelligibility. Severe limb ataxia limited the use of communication boards and augmentative communication keyboards.
          A trial of low-dose oral Clonazepam 1mg BD was given for pharmacological treatment of PM but this was aborted early due to excessive sedation, which interfered with participation in therapy. Fluoxetine 20mg O.M. was also started for concomitant post-stroke depression. No change in her myoclonus was noted on a repeat FEES examination. She was also evaluated by an otolaryngologist for consideration of intramuscular Botulinum toxin A therapy, but this was not carried out due to the widespread muscle involvement and the risk of post-injection bulbar paralysis.
          Prior to discharge, YML was able to ambulate with moderate assistance using a walker and required a moderate level of assistance with self-care activities of daily living. She was also continent. These functional changes represented a significant improvement from her admission functional status. She was discharged home to the care of her husband with a paid caregiver 6 weeks after admission to inpatient rehabilitation.
          FEES examination was repeated at 1 month post-discharge and this showed a reduced delay in her swallow and aspiration occurred on thin liquids only. While this represented an improvement in her swallowing status, her palatal myoclonus was grossly unchanged qualitatively.

DISCUSSION :
          This case illustrates that despite an initial devastating brainstem stroke, late spontaneous recovery at more than 9 months post-stroke, aided by appropriately-timed rehabilitation can result in a positive functional outcome and favourable discharge disposition.
          Horner et al in their cohort of 23 brainstem stroke survivors, reported a dysphagia incidence of 70% using videoflourosopic examination²⁸. Palatal myoclonus is an uncommon accompanying event following a brainstem stroke with few studies documenting its incidence. There is commonly a delay of weeks to several months in the development of PM after a neurological event and the appearance of myoclonus and the precise reason for this delay is not known⁹. The exact pathophysiologic mechanisms for the development of PM after acquired brain injury and its long-term prognosis remain to be established.
          Several postulated mechanisms include lesions or dysfunction of the dentatorubroolivary (Guillain-Mollaret's triangle and Trelle's pathway); and involvement of extrapyramidal lesions^10,11. Enlargement, hypertrophy, neuronal vacuolization and gliosis of the inferior olives either unilaterally or bilaterally have been demonstrated neuropathologically as well as on neuroimaging studies^10-12.
          In this patient, PM had compounded her impaired swallowing function and likely contributed to her dysarthrophonia by preventing sustained voicing and reducing speech intelligibility. The relative contribution of PM to her dysphagia and aspiration over and above her existing swallowing dysfunction post-stroke was not easily determined quantitatively as clinical observations via clinical bedside examinations and FEES visualization were the predominant evaluation tools in this patient. Subtle reductions in the frequency of PM may well have been difficult to detect.
          Speech and dysphagia therapy has been proven to be a useful and safe therapeutic modality for managing dysphagia and preventing aspiration and it's primary medical complication of aspiration pneumonia^26,27. This was the mainstay of dysphagia treatment in this patient and it allowed her to swallow safely and communicate more intelligibly albeit without appreciable change in her PM. Pharmacotherapy was unsuccessful in significantly reducing or abolishing her myoclonus due to cognitive-impairing side effects.
          Current management of PM is unsatisfactory and poorly established. Variable beneficial results have been obtained with medication trials using carbamazepine, Phenytoin, Clonazepam, Benzodiazepines, Anticholinergics, Antidepressants, 5 hydroxytrptophan, L -dopa agonists, Tetrabenezine, opioid agonists, and Sumatripan^13-18. These are based on possible augmentation and inhibition of various central nervous system pathways. Clonazepam is postulated to increase cerebral levels of 5-hydroxytryptamine in order to replenish reduced serotonin metabolites¹⁹. Multiple side effects from high doses of these medications remains a dose-limiting concern and frequent cause of early termination of drug therapy.
          Surgical treatment of PM, which includes disruption of the tensor and levator veli palatini, has also not produced reproducible, beneficial results^20-22. Recently, the use of Botulinum toxin A (BTX-A) to treat movement disorders has added new approaches to reduce or abolish PM. Previous studies have documented the beneficial effects of EMG-guided injections of BTX-A targeted at the tensor veli palatini in abolishing tinnitus caused by essential PM^23,24. Advantages of using BTX-A include its reversibility and safe side-effect profile and relatively low morbidity. Potential problems include the absence of established guidelines for optimal therapeutic dosages in the palatal muscles and the risk of stimulating antibody production with repeated injections^23,24. The use of BTX-A in this patient was risky in view of the multiplicity of muscles involved, which could result in excessive bulbar muscle weakness and worsening dysphagia from BTX overdosage.
          In conclusion, PM may be a contributory factor to neurogenic dysphagia, dysarthria, dysphonia and aspiration. Treatment options although varied, are largely unsatisfactory and PM remains a difficult management problem. Therapy for dysphagia and speech difficulties is both useful and safe, and can improve function independently of its effects on the severity of the palatal myoclonus.

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