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Massachusetts General Hospital Pain Center, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
Address correspondence and reprint requests to Juan Santiago Palma, 1362 Carlton Drive, Glendale, CA 91205. Address email to jsantiagopalma{at}hotmail.com
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Abstract |
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IMPLICATIONS: A 19-yr-old woman with dystonia developed adductor spasms of the vocal cords after the interruption of intrathecal baclofen. Her symptoms resolved after intrathecal baclofen was restored. In patients with dystonia receiving intrathecal baclofen, the onset of dyspnea should prompt the investigation of baclofen withdrawl.
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Introduction |
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TopAbstractIntroductionCase ReportDiscussionReferences |
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-aminobutyric acid (GABA), has been used to reduce muscle tone in patients with spastic hypertonia of cerebral and spinal origin. Baclofen relieves spasticity by activating G-protein linked presynaptic GABAB receptors that hyperpolarize Ia muscle spindle afferent neurons, thereby reducing the number and amplitude of excitatory postsynaptic potentials along the dendrites of 
-motoneurons (1,2). Twenty-five percent of patients who receive oral baclofen for spasticity develop intolerable side effects. In these patients, intrathecal (IT) baclofen is usually considered as an alternative therapy. The IT administration of baclofen reduces side effects such as sedation, drowsiness, and confusion because large concentrations of baclofen are achieved in the spinal cord while the patient receives a smaller total dose of the drug (3).
Over the past decade, a number of authors (4–8) have described serious events after the sudden discontinuation of IT baclofen. Precipitous withdrawal of IT baclofen has been reported to cause seizures, increased spasticity, hyperthermia, exaggerated rebound spasticity, muscle rigidity, rhabdomyolysis, renal failure, disseminated intravascular coagulopathy, and death (4–8). We report a patient with generalized dystonia of unknown etiology who developed respiratory distress attributable to vocal cord spasms after the abrupt discontinuation of IT baclofen infusion.
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Case Report |
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In her early childhood, symptoms of dystonia included slow or uncoordinated movements of the upper and lower extremities. After age 12, her symptoms progressed rapidly and within a few years she became wheelchair bound. An extensive work up of her dystonia failed to reveal any specific etiology. Sequential trials of oral antispastic drugs were ineffective in controlling her dystonic movements. Eight months prior to this hospital admission, a SynchroMed® IT baclofen infusion system (Medtronic Neurological, Minneapolis, MN) was implanted at our institution. IT baclofen markedly improved her muscle tone, her ability to perform daily activities, and assisted with her ambulation. Nine days before the admission, she underwent a surgical revision of the indwelling baclofen pump at our hospital because the pump was mobile and rotating freely within the pump pocket.
On presentation to the emergency room of a hospital other than ours, she complained that the pump was rotating within the pocket, despite the recent revision. Physical examination on admission was remarkable for audible stridor. Neurological examination revealed an increase in muscle tone and deep tendon reflexes in all extremities as compared with routine examinations in the weeks before her admission.
Examination of the lungs revealed no wheezing or rhonchi. Initial work-up focused on pulmonary infection, infection at the pump pocket site, bronchospastic disease, and pulmonary embolism. White blood cell count and serum chemistries were all within normal limits. Chest radiographs and a ventilation perfusion scan showed no abnormalities.
She was admitted to the intensive care unit for multiple episodes of dyspnea and stridor lasting over 1 h. Direct laryngoscopy revealed adductor spasms of the vocal cords without subglottic narrowing or edema. Pump-catheter malfunction was considered as a potential cause of her respiratory problem and she was transferred to our institution. There she was found to have increased muscle tone compared with her baseline and the pump was noted to be freely mobile within the pocket. A dye study performed under fluoroscopy showed a leak at the junction of the pump and the catheter. During surgical exploration a fissure was found in the connection of the pump with the catheter. A new connector was attached and the pump was placed in a new Dacron pouch and secured to the subcutaneous tissue with silk sutures.
After the surgery, IT baclofen was restarted at a rate of 100 µ/day. Before admission she was receiving 165 µ/day. She continued to experience intermittent periods of respiratory distress with episodes of desaturation. These episodes were treated with gentle intermittent positive pressure ventilation using bag and mask with improvement in saturation and relief of her symptoms. Electroencephalographic (EEG) monitoring revealed no epileptiform disturbances. The dose of IT baclofen was gradually increased to 180 µ/day over 2 days. On postoperative day 3 her muscle tone improved and she was able to participate in physical therapy. She did not have any episodes of respiratory distress after postoperative day 4. She was discharged home on postoperative day 9 in stable condition. She has had no further episodes of respiratory distress 6 mo after the surgery.
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Discussion |
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Reasons for abrupt interruption of IT baclofen therapy include catheter malfunction, small volume in the pump reservoir, programming errors, pump malfunction, and end of pump battery life. The implanted IT catheter is the most vulnerable part of the delivery system. The spinal catheter can break, kink, dislodge, or become occluded by fibrosis at the tip of the catheter (10,11). In our patient, IT baclofen withdrawal occurred because of a fissure of the connector at the pump-catheter junction.
Dyspnea in patients with dystonia may result from central nervous system (CNS) disorders, cardiac or pulmonary disorders, anxiety, or excessive and/or desynchronized contractions of the upper airways and vocal cords (12). Other conditions that can cause dyspnea include laryngeal breathing dystonia, drug-induced laryngeal reactions, Parkinson’s disease, asthma-associated laryngeal dysfunction, psychogenic disorders, and gastroesophageal reflux (13).
Stridor is often the most prominent symptom of airway obstruction. Proper management is possible only after a precise diagnosis has been established. The differential diagnosis encompasses lesions throughout the airway tract.
Our patient did not have a history of recent breathing problems and a comprehensive pulmonary evaluation, including physical examination, electrocardiogram, chest radiographs, laboratory studies, and a ventilation-perfusion scan, helped to exclude cardiac and pulmonary causes of dyspnea. Our patient had no history of laryngeal breathing dystonia, gastroesophageal reflux, or Parkinson’s disease. A normal EEG helped to eliminate CNS pathology.
The absence of any explanation for the stridor and dyspnea, the complete resolution of our patient’s respiratory symptoms after the IT baclofen dose was increased to a dose larger than the one she was receiving before her admission to the hospital, and the onset of increased tone before the development of stridor, lead us to consider IT baclofen withdrawal as the cause of the vocal cord spasms. Laryngoscopy could have been useful to evaluate the function of the vocal cords after IT baclofen was restarted but it was not performed because the patient was asymptomatic.
Braun et al. (12) prospectively studied 26 dystonic patients with dyspnea and found during videofluoroscopic evaluation that 88% had upper airway dysfunction. Their findings included incomplete adduction, adductor spasm, and adductor tremor of the vocal cords.
We speculate that our patient may have had a subclinical movement disorder of the upper airway that was unmasked by the sudden interruption of the IT baclofen. Down-regulation of GABAB receptor sensitivity resulting from chronic IT baclofen therapy and the sudden CNS excitation because of the drug withdrawal might explain the acute onset of the vocal cord movement disorder.
All patients receiving IT baclofen therapy are potentially at risk for withdrawal. Prevention of abrupt discontinuation of IT baclofen requires careful implantation techniques, including meticulous attention to the placement of ties at the catheter pump junction and securing the pump to prevent its mobility within the pocket. Later, to prevent sudden withdrawal, the focus should be on preventing errors during the programming and refilling of the pump. Patients should be advised of the importance of keeping scheduled refill visits and should be instructed about the early symptoms of baclofen withdrawal and the need to get medical attention immediately. In patients with dystonia receiving IT baclofen therapy, the onset of dyspnea associated with increase muscle tone should prompt the investigation of baclofen withdrawal.
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