Article Text

Findings that shed new light on the possible pathogenesis of a disease or an adverse effect
Subthalamic nucleus stimulation in Parkinson’s disease is associated with a risk of fixed epiglottis
  1. H Kataoka,
  2. Maya Yanase,
  3. Makoto Kawahara,
  4. Hidehiro Hirabayashi,
  5. Toshiaki Yamanaka,
  6. Makito Hirano,
  7. Satoshi Ueno
  1. Nara Medical University, 840 Shijo-cho, Kashihara, Nara, 634–8522, Japan
  1. hk55{at}naramed-u.ac.jp

Summary

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) alleviates motor disability of patients with Parkinson’s disease (PD). Mental changes and other adverse events are common, but typically transient. Severe complications such as intracerebral haemorrhage or infection are rare, but 6 of 73 patients who underwent STN-DBS died of pneumonia, cardiac failure or pulmonary embolism. We describe a patient with PD who had sudden respiratory difficulty due to a fixed epiglottis after STN-DBS. This symptom was confirmed to be related to STN stimulation on fibre-optic examination of the larynx.

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BACKGROUND

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) alleviates motor disability of patients with Parkinson’s disease (PD). Mental changes and other adverse events are common, but typically transient. Severe complications such as intracerebral haemorrhage or infection are rare,1 but 6 of 73 patients who underwent STN-DBS died of pneumonia, cardiac failure or pulmonary embolism.1 We describe a patient with PD who had sudden respiratory difficulty due to a fixed epiglottis after STN-DBS. This symptom was confirmed to be related to STN stimulation on fibre-optic examination of the larynx.

CASE PRESENTATION

In December 1995, a 76-year-old man noticed slowness of movements. He had moderate parkinsonism, associated with masked face, stooped posture, bradykinesia, right-side-dominant rigidity and resting tremor. Bradykinesia and rigidity responded to treatment with levodopa. In August 2006, he became severely disabled due to “on-off” phenomena and hallucinations while receiving levodopa, cabergoline, pergolide, quetiapine and risperidone. In September, the patient underwent STN-DBS. Because the right stimulator was located slightly medially to the STN, he underwent a second operation to adjust its position in October (fig 1). Motor disability and hallucinations then decreased at the following STN-DBS settings: cathodic bipolar stimulation, 90 μsec pulse width, 1.7 V and 135 Hz frequency. After surgery, the patient was given only levodopa (500 mg/day). Two months later, he had nocturnal snoring with occasional dyspnea. In January 2007, he presented with difficulty in walking due to a painful constriction in the left leg and was admitted. The results of a laboratory workup were normal, except for an increased creatine kinase level (453 mg/dl). The settings for STN-DBS were changed to bipolar stimulation (90 μsec pulse width, 2.0 V and 135 Hz frequency) in the right subthalamic nucleus and monopolar stimulation (90 μsec pulse width, 1.8 V and 135 Hz frequency) in the left subthalamic nucleus. On the third day after admission, he had severe dyspnea despite inhalation of oxygen during the daytime. Fibre-optic examination of the larynx was then performed. The epiglottis covered the top of the trachea. There was no laryngeal oedema. The epiglottis remained firmly fixed on top of the trachea, regardless of whether the patient was supine or sitting. An emergency tracheostomy was performed. One month after admission, we tested whether the DBS settings affected epiglottis position or movement on laryngeal fibre-optic examination. Each stimulation pattern for DBS was applied for at least 5 minutes, separated by intervals of several minutes. The epiglottis firmly covered the top of the trachea when the voltage applied to the right STN was increased (bipolar stimulation, 90 μsec pulse width, 1.8 V and 135 Hz frequency) (fig 1). This stimulation pattern produced stridor and painful inversion of the left foot, with flexion of the left second to fifth toes and extension of the left great toe. By contrast, the epiglottis was elevated when the voltage was decreased (bipolar stimulation, 90 μsec pulse width, 1.5 V and 135 Hz frequency) (fig 1). The settings in the left STN remained constant during this investigation–that is, monopolar stimulation (90 μsec pulse width, 1.8 V and 135 Hz frequency). He could say words without hoarseness during the procedure, suggesting that his vocal cords were not severely paralysed. Speech type during the stimulation was not ataxic, but rather “parkinsonistic.” However, these settings subsequently caused similar adverse events. In April, he could walk alone at the following DBS settings: monopolar right stimulation, 60 μsec pulse width, 1.5 V and 135 Hz frequency; and monopolar left stimulation, 90 μsec pulse width, 1.8 V and 135 Hz frequency. Follow-up fibre-optic examination of the larynx showed that the epiglottis still covered the trachea, but the patient rarely had pain in the left lower limb

Figure 1 Epiglottis during subthalamic nucleus-deep brain stimulation (STN-DBS) under two conditions.

Left panel: Coronal MRI showing that the top of the right DBS lead was implanted just medially to the STN. Middle panel (cathodic bipolar stimulation, 90 μsec pulse width, 1.8 V, 135 Hz frequency): The epiglottis covered the top of the trachea. Right panel (cathodic bipolar stimulation, 90 μsec pulse width, 1.5 V, 135 Hz frequency): the epiglottis did not cover the trachea.

DISCUSSION

We described a patient with PD who had respiratory difficulty caused by a fixed epiglottis after STN stimulation. Fibre-optic examination of the larynx confirmed that fixation of the epiglottis was aggravated by increasing the voltage of the STN stimulator and was immediately relieved by decreasing the voltage. Although a fixed epiglottis has not previously been documented as an adverse event of STN stimulation or as a parkinsonian symptom, a causal association with STN stimulation was established on fibre-optic examination of the larynx.

Delineation of the specific types of involuntary movements that were related to the fixed epiglottis in our patient may help to identify underlying causes. One stimulation-related sign–painful inversion of the left foot with flexion of the second to fifth toes and extension of the great toe–was similar to the foot dystonia seen in some patients with PD.2 Stridor associated with PD is referred to as “laryngeal dystonia”.3 These facts and the finding that the epiglottis was firmly fixed regardless of body position suggested that dystonia was involved.

Why STN stimulation caused dystonia remains uncertain, as dystonia is generally suppressed by this technique. Acute high-frequency STN stimulation similar to that used in our patient is particularly effective.2 However, high voltages have induced repetitive dystonic dyskinesias, with further increases in voltage leading to a shift from dystonia to choreodystonia, corresponding to STN hypoactivity induced by high-voltage, high-frequency stimulation.2 Another STN stimulation study showed that a voltage and frequency exceeding a certain threshold induced ballistic movements or dystonia.4 Dystonia in our patient may have been caused by increased dysequilibium of thalamocortical circuits in basal ganglia due to high-frequency STN stimulation. However, we cannot exclude other mechanisms, as speech impairment has been associated with DBS-induced irritation of adjacent fibre tracts,5 including the corticobulbar tract that is lateral to the STN and the cerebellar-thalamic tract that is medial to the STN. Further studies are therefore needed to clarify whether isolated or combined mechanisms contributed to fixed epiglottis.

In PD, sudden death can occur due to fatal arrhythmias associated with QT-interval prolongation on electrocardiography or vocal-cord adductor paralysis. Although limited, our experience suggests that STN stimulation, especially with a high voltage, may carry the risk of sudden respiratory difficulty.

LEARNING POINTS

  • A fixed immobile epiglottis occurred in a patient with Parkinson’s disease in response to stimulation of the subthalamic nucleus.

Acknowledgments

This article has been adapted with permission from Yanase M, Kataoka H, Kawahara M, Hirabayashi H, Yamanaka T, Hirano M, Ueno S. Fixed epiglottis associated with subthalamic nucleus stimulation in Parkinson’s disease. J Neurol Neurosurg Psychiatry 2008;79:332–3.

REFERENCES

Footnotes

  • Competing interests: None.

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