Kinesigenic dyskinesias after ENT surgery misdiagnosed as focal epilepsy

Abstract

We describe a man in his 30s who presented with paroxysmal right-sided dyskinesias of the arm and neck, misdiagnosed with drug-resistant focal epilepsy. Two months earlier he had undergone surgery for chronic sinusitis. Immediately after this procedure, he developed hemiparesis, hemiataxia, paresthesias and disturbances in verbal fluency. Cranial MRI revealed a disruption of the left lamina cribrosa and an intracerebral injury resembling a branch canal spanning to the left dorsal third of the thalamus. Single-photon emission tomography imaging demonstrated malperfusion of the left ventral thalamus, left-sided cortex and right cerebellar hemisphere. During continuous video-EEG monitoring, three dyskinetic episodes with tremor of the right arm and dystonia of the finger and shoulder could be recorded. The paroxysmal dyskinesias did not improve with carbamazepine, valproate and tiapride. This case demonstrates an unusual symptomatic cause of a thalamic movement disorder misdiagnosed as focal epilepsy and highlights the postoperative complications, diagnostic and treatment efforts.

Background

It is well established that thalamic lesions may lead to various symptoms including sensorimotor deficits and movement disorders.^1–3 However, reports about iatrogenic thalamic lesions are scarce. Here, we present a patient with a thalamic movement disorder, in whom the iatrogenic thalamic lesion manifested as a complication of ear, nose and throat (ENT) surgery.

Case presentation

The patient’s complaints were a paroxysmal right-sided tremor and dyskinesias occurring about three times a day for 2 months, in particular when exerting strenuous activities. Transient right-sided paresis and paresthesias for 4 months occurred immediately after ENT surgery for chronic sinusitis.

Four months prior to admission, an ENT surgery for chronic sinusitis with septum plastic, bilateral conchotomy, polyp removal and endoscopic supported pansinusitis surgery had been performed. Immediately after surgery the patient reported paresthesias and right-sided hemiparesis. The hemiparesis improved over the course of weeks but did not subside completely. Two months after the surgery, rhythmic jerks of the right arm and right side of the neck occurred three times a day for several minutes. The patient was referred to a regional hospital, where an epileptic origin of the ‘convulsions’ was suspected resulting in a prescription of carbamazepine 800 mg/day.

As the rhythmic jerks continued, the patient was admitted to the epilepsy centre of the regional university hospital, where right-sided hemiparesis, paresthesias and anosmia were documented. At this point in time, three to six times a day, paroxysmal, rhythmical dyskinetic attacks of 1–2 min duration in the right hand and occasionally also in the whole right arm occurred. Most attacks were provoked by strenuous motor activities.

Investigations

Clinical examinations and motor evoked potentials yielded no evidence supporting a lesion of the pyramidal tracts. Somatosensory evoked potentials indicated central axonal damage after right-sided stimulation (figure 1). Neuropsychological examination showed a severe deficit in verbal memory and fluency. A video electroencephalography (EEG) of 8 hours duration showed three dyskinetic episodes with tremor of the right arm and dystonia of the fingers and partly the shoulder. Two episodes were provoked by kneading a foam cushion wedge with the right arm and one episode occurred spontaneously. The tremor increased when holding up the arm or when attempting aimed movements and completely remitted by resting the arm (Video 1). The EEG showed no signs of event-related potentials.

Figure 1.

Somatosensory evoked potential (SEP) results reflect the left thalamic lesion.

Video 1.

bcr-2021-247760supp001.mp4 ^{(668.9KB, mp4)}

DOI: 10.1136/bcr-2021-247760.video01

During one dyskinetic episode, 4 s after onset, a technetium-99m (^99mTc) tracer was injected for single-photon emission tomography (SPECT) imaging. The ^99mTc-SPECT imaging reflects the cerebral perfusion state around the time of injection and revealed a malperfusion of the left ventral thalamus, left-sided cortex and a crossed cerebellar diaschisis, that is, a hypoperfusion of right cerebellar hemisphere. CT imaging showed an approximately 5 mm wide disruption of the left lamina cribrosa. MRI demonstrated a bony defect in the left gyrus rectus adjoining an approximately 4,5 cm long intracerebral lesion spanning to the dorsal third of the thalamus in the area of the corticospinal tract with some bleeding residues (figures 2 and 3).

Figure 2.

T2-weighted MRI imaging in coronal plane demonstrating an intracerebral defect in the left gyrus rectus.

Figure 3.

Gradient echo-weighted MRI imaging in axial plane demonstrates the intracerebral lesion spanning to the dorsal third of the left thalamus with some bleeding residues.

Differential diagnosis

As the EEG showed no signs of epilepsy and the patient was able to partly suppress and induce the dyskinesias of the arm, focal epilepsy was an unlikely differential diagnosis. The dyskinetic movements may be classified as kinesigenic dyskinesias or a dystonic tremor. However, the kinesigenic dyskinesia is more likely as the lesion also involved the left subthalamic nucleus. The nucleus subthalamicus sends inhibitory signals to the inhibitory motor parts of the globus pallidum leading to suppression of the ventroanterior and ventrolateral nuclei of the thalamus. Therefore, a lesion of the nucleus subthalamicus may result in hyperkinetic symptoms on the contralateral side.

Treatment

Valproate was started and as soon as its target concentration of 50–100 µg/mL was reached, carbamazepine was discontinued due to lack of symptom improvement. The patient stayed at a rehabilitation hospital on three separate occasions. According to the patient, neither of the two medications nor tiapride improved the attacks but caused side effects such as dizziness, leading to the discontinuation of the drugs.

For paroxysmal kinesigenic dyskinesias, sodium channel blockers such as carbamazepine are the recommended treatment.^4–7 Especially in patients with primary paroxysmal kinesigenic dyskinesias, which are considered to be hereditary, carbamazepine has shown good effects.⁸ However, in secondary paroxysmal kinesigenic dyskinesias like our case, sodium channel blockers have not shown similarly consistent results.⁷ Yet, some case reports show good efficacy of carbamazepine in improving dyskinesias secondary to thalamic lesions caused by stroke and multiple sclerosis.^{9 10} There are scarce reports about valproate treatment in paroxysmal kinesigenic dyskinesias and even in those reports, it was not the first choice of treatment.^{4 7}

Outcome and follow-up

The kinesigenic dyskinesias slightly improved spontaneously, as the dyskinesias in the right arm occurred less frequently over time. However, 18 years later, the patient still suffers from right-sided fine motor difficulties, as well as right-sided paresthesias and slight weakness. As the patient is right-handed, he learnt to use his left hand predominantly. He works part-time as a caregiver in an institution for people with disabilities.

Discussion

Thalamic movement disorders may phenotypically present as dyskinesias, which may be further classified into subcategories such as dystonia, chorea, (haemi-)ballism, athetosis, tremor, myoclonus or asterixis.^11–14

We discuss a rare case of a man in his 30s with thalamic movement disorder presenting as kinesigenic dyskinesias after iatrogenic thalamic damage due to ENT surgery.

The thalamus is considered the relay station for information processing through the brain as it receives afferent fibers from basal ganglia and cerebellum and sends projections to the cortex (figure 4).¹⁵ Disturbance of the cerebellar-thalamic loop and the cortico-striato-pallido-thalamo-cortical loop can lead to a loss of inhibition at cortical level and cause movement disorders.^{11 16–19} A lesion of the nucleus subthalamicus may impair inhibition of thalamus and result in dyskinesias.²⁰

Figure 4.

The simplified sketch shows the cerebello-thalamic loop on the left and the cortico-striato-pallido-thalamo-cortical loop on the right. The green arrows demonstrate glutamatergic excitation and the red arrows with a blunt end GABAergic (y-aminobutyric acid-ergic) inhibition. The red blizzard icons symbolise the lesion locations in our patient. Globus pallidus ext., globus pallidus externus; globus pallidus int., globus pallidus interneus; Nuc. subthalamicus, nucleus subthalamicus. The figure was created by SDT.

As neuroanatomy dictates, in the thalamus dyskinesias are described to mainly originate from damage to the ventroanterior, ventrolateral,¹⁷ posterior, posterolateral^{14 21} and dorsolateral thalamic nuclei.²²

Kinesigenic dyskinesias present with dyskinetic movements triggered by voluntary movement typically involving the extremities.^{23 24} Similar to our case, acquired thalamic lesions have been described to cause dyskinesias months after damage;^{13 25} however, most frequently, those lesions are of vascular origin.^1–3 There are only limited reports about iatrogenic thalamic lesions. One case report describes three tremor patients who permanently suffered from dystonia after radiofrequency thalamotomy and deep brain stimulation (DBS) to the right nucleus ventralis intermedius.¹⁸ Further, dyskinesia is a known, rare and usually reversible complication of DBS of the subthalamic nucleus.^{20 26} On the other side, strategic lesioning of the internal part of globus pallidus internus or subthalamic nucleus or functional lesioning using DBS has been established as treatment option for treatment-resistant movement disorders including dyskinesia.^{27 28} This suggests that maybe the aetiology, precise location and especially size of the thalamic lesion might be crucial for the induction or improvement of dyskinesia.

A retrospective study examined 29 patients with Holmes tremor and observed that all included patients with dystonia (n=16) showed thalamic involvement. Besides dystonia, they also presented hemiparesis (75%), hypesthesia (25%) and cerebellar symptoms (25%).²⁹ Similarly, our patient presented with right-sided hemiparesis which may be explained by axonal damage of the corticospinal tract. As the thalamus receives sensory signals from spinothalamic tract and afferences from sensory cranial nerves, damage may also lead to right-sided paresthesias. The crossed cerebellar diaschisis causes a phenomenon of cerebellar malperfusion secondary to contralateral thalamic damage and possibly explains the right-sided hemiataxia of this patient.³⁰

Neuropsychological examination revealed verbal memory and fluency deficits in this patient, possibly caused by the malperfusion in the area of the ventral anterior thalamus due to the lesion spanning until the dorsal thalamus. Several studies have suggested an association of Broca’s area and ventral anterior nucleus of the thalamus.^31–33

Medical treatment typically includes carbamazepine as first-line therapy which has good effect in primary paroxysmal kinesigenic dyskinesias, but was shown to be less effective in those with a secondary cause, similar to our case.^4–7 Furthermore, phenytoin,^{5 6 34} topiramate^{34 35} and zonisamide³⁶ were in some cases successfully used in doses lower than typically used for epileptic seizures. Acetazolamide,^{5 6 37} levodopa, tetrabenazine and trihexyphenidyl hydrochloride^{5 37} have similarly shown promising results, although in a limited number of cases.

Learning points.

• Complications of ENT surgery may cause thalamic movement disorders.

• Unclassified movement disorders may require multimodal evaluation including video-EEG monitoring.

• Ventral thalamic lesions may cause kinesigenic dyskinesias.

Ethics statements

Patient consent for publication

Consent obtained directly from patient(s).