Tourette syndrome and epilepsy are common illnesses in childhood. ^{Reference Fisher, van Emde Boas and Blume1} Tourette syndrome is characterized by involuntary motor and vocal tics, which persist for at least one year. The underlying mechanism of this illness is not elucidated; however, both basal ganglia hyperactivity and social network pathways are thought to be critical. ^{Reference Albin2} Epileptic seizures are characterized by transient excessive synchronous neuronal cortical activity. The rate of epilepsy in children with Tourette syndrome is 18-fold higher than in patients without Tourette syndrome, although the connection between these pathologies remains unclear. ^{Reference Fisher, van Emde Boas and Blume1} Herein, we present a patient with drug-resistant epilepsy and Tourette syndrome who had transient resolution of their tics following dominant mesial anterior temporal lobectomy (ATL) to treat their epilepsy.

Our patient is a 23-year-old right-handed male with Tourette syndrome with a 7-year history of focal seizures. His seizure semiology involved sequentially an aura of lightheadedness, rising epigastric sensation, pallor and diaphoresis, followed by impaired awareness and activity arrest. Occasionally, he had focal to bilateral tonic-clonic seizures lasting 1to 2 minutes, followed by postictal fatigue for several hours. His only epilepsy risk factor was developmental delay. He read at a grade 2 to 3 level, while his verbal comprehension and arithmetic skills were scored at a grade 2 level. He was diagnosed with Tourette syndrome at age 7 years with persistent severe motor tics involving turning his head to either side, neck flexion/extension, facial gestures and upper limb grabbing/pulling movements and repeateitive throat-clearing vocal tics. Due to severe tics, he avoided social interactions.

His seizures were treated with a combination of carbamazepine, lamotrigine and clobazam. Despite adhering to this medication regimen, he continued experiencing focal impaired awareness seizures multiple times a week.

Given his drug-resistant epilepsy, he underwent a presurgical workup. His brain MRI demonstrated extensive malformation of cortical development in the frontal lobes bilaterally with associated pachygyria and left hippocampal atrophy. In addition, there was polymicrogyria in the left frontotemporal region and diffuse atrophy of the left hemisphere. An interictal FDG-PET scan demonstrated left temporal hypometabolism involving the mesial structures. His routine electroencephalogram demonstrated left anterior temporal epileptiform discharges, and his typical seizures started in the left temporal region, which were captured on prolonged inpatient video-electroencephalogram recording. His neuropsychological battery identified intellectual disability, without clear lateralization of his cognitive deficiencies. He underwent a functional brain MRI demonstrating a left hemispheric typical localization for language, which was also confirmed by WADA testing.

Given his concordant findings on imaging and electroencephalogram, the patient underwent a left ATL, with a 4.5 cm anterior to posterior length of the tissue, which included the middle and inferior temporal gyri. He had no surgical complications. With his residual extensive cortical malformation, his prognosis for complete seizure resolution was guarded. His mesial temporal structures were fully removed as part of the ATL. His language remained at baseline after the left ATL (his resection was language sparing with the limited depth of resection).

After his procedure, he was seizure free for 4 weeks, which was followed by monthly focal impaired awareness seizures with the same semiology as his original seizures, save for the evolution to tonic-clonic movements. He had a complete resolution of all tics for 6 weeks without any medication changes. However, after 6 weeks, his motor and vocal tics reemerged and gradually progressed to their original intensity.

This is the first report of a neurosurgical resection leading to transient resolution of severe motor and vocal tics. In contrast to this case of improved tic control following dominant ATL, there are two pre-existing case reports of exacerbation of tic disorders following nondominant anterior temporal lobe resections for epilepsy. ^{Reference Liu, Miao and Wang8} The differing outcomes may relate to hemispheric lateralization with a differential contribution of dominant and nondominant hemispheres to tic disorders, particularly the anteromesial temporal lobes. In contrast, the subtle difference in depth of resection between hemispheres, with larger resections in nondominant ATLs, involves similar structures and is unlikely to explain these divergent effects on tic control.

Another potential contributor to tic severity is seizure control. Both prior case reports of worsened tic severity following ATL suggested “forced normalization” with improvement of seizure control, as a possible mechanism for tic exacerbation. ^{Reference Chemali and Bromfield3,Reference Sinno, Al-Amin, Comair and Mikati4} However, the concordant improvements in seizure and tic control in our case suggests the possibility that nondominant hemispheric seizures reduce tic severity while dominant hemisphere seizures exacerbate tics. The correlation between seizure activity and tic control would be consistent with the coincident re-emergence of tics and recurrent seizures in our patient.

We hypothesize that the mesial temporal lobes are important modulators of tic control (Figure 1). We suspect the dominant and nondominant lobes have opposing influences (Figure 1A), with suppression of tics after dominant ATL (Figure 1B) and exacerbation of tics with nondominant ATL (Figure 1C). These resections include the amygdala, a structure implicated in Tourette syndrome pathophysiology, which modulates interactions between the social behavior network and mesolimbic reward systems, which together drive tics. ^{Reference Albin2} The brain’s social behavior network is comprised of the medial amygdala, medial bed nucleus of stria terminalis, lateral septum, preoptic area, anterior hypothalamus, ventromedial hypothalamus, periaqueductal gray, and the midbrain tegmentum, interacting with basal (limbic) forebrain. ^{Reference Newman5,Reference Goodson6} Tic modulation may reflect the impact of the mesial temporal structures on social behavior.

Figure 1. Proposed schematic model (using simplified schematic⁴) of influence of anterior temporal resection on tic disorder severity. (A) The interaction of the anterior temporal lobes within the social behavioural network and mesolimbic reward system with baseline control. Tic enhancement by the dominant hemisphere and suppression by the nondominant hemisphere are in balance. (B) The resection of the tic-promoting dominant anterior temporal lobes results in improved tic control. (C) The resection of the tic-inhibiting nondominant anterior temporal lobes results in exacerbation of tic control.

Lateralization of cerebral abnormalities in patients with tics has been demonstrated on functional imaging showing asymmetry in the basal ganglia metabolism and structural imaging showing asymmetric brain volume changes. ^{Reference Braun, Stoetter and Randolph7,Reference Liu, Miao and Wang8} Greater right hemispheric brain volume loss correlates with worse tic control. ^{Reference Liu, Miao and Wang8} A lateralized etiology of tics is important for interventions to treat refractory cases of Tourette syndrome. Deep brain stimulation of the amygdala has been suggested as a potential target, ^{Reference Sinno, Al-Amin, Comair and Mikati4} with our analysis highlighting that the dominant hemisphere may be an ideal target. Noninvasive neuromodulation (e.g.: transcranial magnetic stimulation or transcranial direct current stimulation) of targets in the dominant hemisphere may also provide therapeutic benefit. Lastly, the potential alteration in tic severity after temporal lobe epilepsy surgery may warrant discussion for patients with refractory epilepsy and comorbid tics.

We describe a patient with improvement in his tics following dominant ATL, which contrasts two prior reports of tic exacerbations in patients with nondominant ATL. We hypothesize that the mesial temporal structures (specifically the amygdala) play an important role in tic neurocircuitry, with stimulatory inputs from the dominant temporal lobe to the basal social network system and inhibitory inputs from the nondominant temporal lobe. This case suggests that lesioning or modulating the dominant anterior temporal region could have therapeutic potential in patients with refractory and bothersome tics.