“Rubral” Tremor after Cardiac Catheterization

Abstract

The so-called rubral tremor is a clinical diagnosis that involves involuntary shaking limb movements during rest and voluntary motion. We report the cases of 2 patients who developed rubral tremor after cardiac catheterization. To our knowledge, this is the 1st report of such an association. In each case, brain magnetic resonance imaging revealed nothing unusual.

The onset of tremor after cardiac catheterization may signal the presence of a complex neurologic syndrome, which warrants consultation with a neurologist.

The ever-expanding field of cardiology has placed cardiologists at the interface of several medical disciplines, including neurology. In particular, cardiac procedures occasionally result in neurologic complications that require prompt recognition by the cardiologist. “Rubral” tremor (RT) is a clinical diagnosis characterized by the triad of resting, static, and kinetic involuntary shaking of the limbs. Rubral tremor shares similarities with both parkinsonian and cerebellar tremors and is classically associated with lesions affecting the midbrain or the thalamus.^1,2 However, in some patients, no apparent cause of tremor can be identified, even after extensive evaluation. Herein, we describe 2 cases of RT, hemiparesis, and ataxia that occurred after cardiac catheterization for diagnostic coronary angiography.

Case Reports

Patient 1

A 78-year-old man presented at the Washington, DC, Veterans Affairs Medical Center with a tremor of gradual onset that was interfering with the use of his dominant (right) hand. He had also developed a stutter. Similar symptoms had occurred 8 months earlier, a few hours after cardiac catheterization, and had lasted about a week. A neurologist examined the patient at that time and made the diagnosis of RT. The patient was also experiencing right-sided weakness and gait difficulties.

He had a history of coronary artery disease, hypertension, and type 2 diabetes mellitus. He had previously undergone coronary artery bypass surgery, percutaneous transluminal coronary angioplasty, and right carotid endarterectomy (for asymptomatic stenosis). His medications included furosemide, hydrochlorothiazide, lisinopril, diltiazem, aspirin, glyburide, and simvastatin. The patient had not stuttered before and, in fact, had been a radio announcer and singer at a younger age. He had consumed alcohol and smoked cigarettes in the past but had never used illicit drugs.

The neurologic examination revealed hesitant speech with a tremulous quality of the voice. The soft palate displayed slow, irregular, and involuntary contractions at a rate of 10 per minute. The patient had discrete pronator drift, right leg circumduction, and spasticity on the right side. Plantar responses were absent. There was mild right-sided limb ataxia. A coarse, fast, bilateral resting tremor was noted (more intense on the right side), which worsened with movement.

Laboratory test results are presented in Table I. New cardiac catheterization revealed patency of all grafts. Results of a myocardial perfusion study with radioisotopes were normal, as were the results of magnetic resonance imaging (MRI) of the brain. The electroencephalogram demonstrated mild generalized slowing. A temporal artery biopsy was obtained because of an ele-vated erythrocyte sedimentation rate and occasional headaches, but no giant cells were seen. The elevated sedimentation rate was attributed to severe knee degenerative arthritis. Trials of clonazepam, primidone, and levodopa partially alleviated the tremor. Follow-up MRI, 4 months after our initial evaluation, showed no change. The symptoms gradually improved over 1 year and currently surface only during periods of emotional upset.

TABLE I. Ancillary Investigation in 2 Patients with Rubral Tremor

Patient 2

A 72-year-old man experienced the abrupt onset of hand tremor, more on the right side, 1 day after cardiac catheterization. The tremor hindered the use of his dominant (right) hand. His medical history included coronary artery disease and hypercholesterolemia. He had undergone triple-vessel percutaneous transluminal coronary angioplasty 2 years earlier. His medications included aspirin and atorvastatin. He did not consume alcohol, smoke, or use illicit drugs.

The physical examination revealed a fast, coarse tremor at rest that worsened with voluntary movements, especially on the right side. Right leg circumduction and decreased arm swing were observed on the right side, as well as limb ataxia with dynamic arm oscillation (more on the right). Global areflexia but normal plantar responses were noted. Results of an MRI of the brain and a magnetic resonance angiogram of the craniocervical vasculature were normal. A new coronary angiogram showed patency of the stents. Results of laboratory tests are presented in Table I. No therapy for the tremor was administered; spontaneous remission occurred after a few months.

Discussion

We have described 2 cases of RT that occurred within a day after conventional cardiac angiographic procedures. To our knowledge, this is the 1st report of such an association. The striking coincidence of cardiac catheterization and onset of symptoms suggests a cause-and-effect relationship. It is possible that either the contrast media or embolization of débris during manipulation of the endovascular catheter precipitated the RT. Adverse reactions—usually minor vasomotor symptoms—occur in approximately 5% of patients receiving intravascular contrast material.³ Other sequelae include nausea, vomiting, paresthesias of the extremities, and reversible cortical blindness.³

The incidence of neurologic complications after cardiac catheterization is 0.03% to 0.4%.⁴ Ischemic stroke during cardiac catheterization appears to preferentially affect the vertebrobasilar circulation. Transcranial Doppler ultrasonography of the middle cerebral arteries has revealed that clinically silent microembolic signals are common during cardiac catheterization.⁵ Emboli can consist of air, platelet clusters, fibrin, atheromatous material, or a combination of these.⁵ Being female, having left ventricular hypertrophy, or having a low left ventricular ejection fraction are predisposing factors.⁴ The incidence of vascular occlusive complications is similar between ionic and nonionic contrast materials.⁶

Despite the normal results of the brain MRIs, we speculate that our patients sustained small ischemic lesions in the posterior circulation, perhaps due to emboli arising from the heart or the ascending aorta during cardiac catheterization. The failure of MRI to detect brain parenchymal abnormalities can be attributed to the inherent limitations of the technique, which may not detect lesions smaller than 5 mm (we used 1.5 Tesla scanners). In addition, we did not obtain diffusion-weighted imaging sequences, and the sensitivity of conventional MRI may have been insufficient to rule out focal lesions caused by acute brain ischemia. Conventional MRI sequences are expected to detect most brain ischemic lesions when performed 8 to 24 hours after the onset of symptoms.⁷ However, in our patients, the MRI examinations were performed more than 24 hours after the onset of symptoms.

Rubral tremor is a clinical diagnosis (similar to Parkinson's disease), and its presence does not necessarily suggest an underlying brain parenchymal lesion. The tremor is usually unilateral and may be accompanied by hemiparesis, hemiataxia, bradykinesia, 3rd cranial nerve palsy, and palatal myoclonus (also called palatal tremor, characterized by involuntary and irregular movements of the soft palate).^8–11 Although the term rubral tremor suggests dysfunction of the red nucleus, experimental lesions of this particular group of midbrain neurons do not produce tremor in animals.^8,9 The pathophysiology of RT involves dysfunction of nigrostriatal and cerebellorubral outflow pathways, which explains the resting and kinetic components of the tremor, respectively.^11,12 Positron emission tomographic scanning with 18F-fluorodopa uptake has demonstrated severe unilateral dopaminergic denervation in the striatum of patients with RT, indicating dysfunctional nigrostriatal pathways.¹² However, therapy with levodopa alone does not suppress RT, or may only ameliorate the resting tremor component, suggesting a concomitant disruption of the neighboring cerebello-thalamic and cerebello-olivary tracts.¹² It is conceivable that diminutive embolic particles (microemboli, or particles smaller than 200 μm) could cause decompensation of a vulnerable neuronal system.¹³ For instance, the marginal function of neurons within the substantia nigra of a patient with preclinical parkinsonism could suddenly fail after a moderate but abrupt drop in the number of functional neighboring neurons, as a consequence of an acute superimposed injury.

We conclude that RT is a rare complication of cardiac catheterization. Although the clinical course was benign in our patients, the RT required neurologic consultation, diagnostic neuroimaging, and empiric pharmacologic therapy.