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Dirk De Ridder, Kathleen Joos and Sven Vanneste

Tinnitus can be distressful, and tinnitus distress has been linked to increased beta oscillatory activity in the dorsal anterior cingulate cortex (dACC). The amount of distress is linked to alpha activity in the medial temporal lobe (amygdala and parahippocampal area), as well as the subgenual (sg)ACC and insula, and the functional connectivity between the parahippocampal area and the sgACC at 10 and 11.5 Hz.

The authors describe 2 patients with very severely distressing intractable tinnitus who underwent transcranial magnetic stimulation (TMS) with a double-cone coil targeting the dACC and subsequent implantation of electrodes on the dACC. One of the patients responded to the implant and one did not, even though phenomenologically they both expressed the same tinnitus loudness and distress.

The responder has remained dramatically improved for more than 2 years with 6-Hz burst stimulation of the dACC. The 2 patients differed in functional connectivity between the area of the implant and a tinnitus network consisting of the parahippocampal area as well as the sgACC and insula; that is, the responder had increased functional connectivity between these areas, whereas the nonresponder had decreased functional connectivity between these areas. Only the patient with increased functional connectivity linked to the target area of repetitive TMS or implantation might transmit the stimulation current to the entire tinnitus network and thus clinically improve.

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Dirk De Ridder and Tomas Menovsky

✓Isolated abducent palsy is a symptom that can be caused by many different intracranial pathological conditions. In this report the authors describe the case of a patient who suffered isolated abducent palsy resulting from vascular compression of the sixth cranial nerve; surgical treatment consisted of microvascular decompression (MVD).

This 56-year-old man presented with short-lasting episodes of a pulling sensation at the lateral side of his right eye associated with intermittent diplopia, followed by a progressive palsy of the abducent nerve and constant diplopia. Magnetic resonance imaging revealed a neurovascular contact of a dolichoectatic basilar artery with the abducent nerve. The patient underwent surgery consisting of a combined supra- and infratentorial presigmoid approach and subsequent MVD of the abducent nerve. Postoperatively, the abducent nerve palsy resolved within days, and the patient remains free of symptoms with a follow-up time of 4 years.

This is the first report of a neurovascular compression of the abducent nerve treated successfully by MVD.

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Dirk De Ridder, Gert De Mulder, Vincent Walsh, Neil Muggleton, Stefan Sunaert and Aage Møller

✓ Tinnitus is a distressing symptom that affects up to 15% of the population for whom no satisfactory treatment exists. The authors present a novel surgical approach for the treatment of intractable tinnitus, based on cortical stimulation of the auditory cortex.

Tinnitus can be considered an auditory phantom phenomenon similar to deafferentation pain, which is observed in the somatosensory system. Tinnitus is accompanied by a change in the tonotopic map of the auditory cortex. Furthermore, there is a highly positive association between the subjective intensity of the tinnitus and the amount of shift in tinnitus frequency in the auditory cortex, that is, the amount of cortical reorganization. This cortical reorganization can be demonstrated by functional magnetic resonance (fMR) imaging.

Transcranial magnetic stimulation (TMS) is a noninvasive method of activating or deactivating focal areas of the human brain. Linked to a navigation system that is guided by fMR images of the auditory system, TMS can suppress areas of cortical plasticity. If it is successful in suppressing a patient's tinnitus, this focal and temporary effect can be perpetualized by implanting a cortical electrode.

A neuronavigation-based auditory fMR imaging-guided TMS session was performed in a patient who suffered from tinnitus due to a cochlear nerve lesion. Complete suppression of the tinnitus was obtained. At a later time an extradural electrode was implanted with the guidance of auditory fMR imaging navigation. Postoperatively, the patient's tinnitus disappeared and remains absent 10 months later.

Focal extradural electrical stimulation of the primary auditory cortex at the area of cortical plasticity is capable of suppressing contralateral tinnitus completely. Transcranial magnetic stimulation may be an ideal method for noninvasive studies of surgical candidates in whom stimulating electrodes might be implanted for tinnitus suppression.

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Dirk De Ridder, Giovanni Alessi, Marc Lemmerling, Hendrik Fransen and Luc De Waele

✓ Hemilingual spasm is a little-known movement disorder, presenting as intermittent paroxysmal involuntary contractions of half of the tongue muscles. The authors report a case of hemilingual spasm caused by an arachnoid cyst. After marsupialization of the cyst, the patient's symptoms immediately resolved. There has been no recurrence of hemilingual spasm during the follow-up period of more than 40 months.

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Dirk De Ridder, Guy Hans, Philippe Pals and Tomas Menovsky

A 56-year-old man presented to the outpatient clinic with a 3-year history of itch within the innervation territory of C-6 of the left arm. Sudden neck movements induced intermittent paresthesias in the same dermatome. No dermatological diseases, allergies, or trauma to the affected extremity or the spine or a history of familial pruritus were reported.

Neurological physical examination and electromyography revealed normal findings. Quantitative sensory testing demonstrated selective C-fiber dysfunction at C6–8 on the left, and cervical MR imaging revealed multilevel degenerative cervical spine pathology with neuroforaminal stenoses. Brachioradial neuropathic pruritus caused by cervical neuroforaminal stenosis was the final diagnosis. Treatment consisted of 2 cervical epidural steroid applications that resulted in clinical disappearance of the itch and improvement in C-fiber function on quantitative sensory testing.

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Katrin Van Loock, Mark Plazier, Dirk De Ridder and Tomas Menovsky

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Dirk De Ridder, Sven Vanneste, Elsa van der Loo, Mark Plazier, Tomas Menovsky and Paul van de Heyning


Tinnitus is an auditory phantom percept related to tonic and burst hyperactivity of the auditory system. Two parallel pathways supply auditory information to the cerebral cortex: the tonotopically organized lemniscal system, and the nontonotopic extralemniscal system, which fire in tonic and burst mode, respectively. Electrical cortex stimulation is a method capable of modulating activity of the human cortex by delivering stimuli in a tonic or burst way. Burst firing is shown to be more powerful in activating the cerebral cortex than tonic firing, and bursts may activate neurons that are not activated by tonic firing.


Five patients with an implanted electrode on the auditory cortex were asked to rate their tinnitus distress and intensity on a visual analog scale before and after 40-Hz tonic and 40-Hz burst (5 pulses at 500 Hz) stimulation. All patients presented with both high-pitched pure tone and white noise components in their tinnitus.


A significantly better suppression for narrowband noise tinnitus with burst stimulation in comparison with tonic stimulation (Z = −2.03, p = 0.04) was found. For pure tone tinnitus, no difference was found between tonic and burst stimulation (Z = −0.58, p = 0.56). No significant effect was obtained for stimulation amplitude (Z = −1.21, p = 0.23) and electrical charge per pulse (Z = −0.67, p = 0.50) between tonic and burst stimulation. The electrical current delivery per second was significantly different (Z = −2.02, p = 0.04).


Burst stimulation is a new form of neurostimulation that might be helpful in treating symptoms that are intractable to conventional tonic stimulation. Further exploration of this new stimulation design is warranted.

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Dirk De Ridder, Sven Vanneste, Silvia Kovacs, Stefan Sunaert, Tomas Menovsky, Paul van de Heyning and Aage Moller


Tinnitus is a prevalent symptom, with clinical, pathophysiological, and treatment features analogous to pain. Noninvasive transcranial magnetic stimulation (TMS) and intracranial auditory cortex stimulation (ACS) via implanted electrodes into the primary or overlying the secondary auditory cortex have been developed to treat severe cases of intractable tinnitus.


A series of 43 patients who benefited transiently from 2 separate placebo-controlled TMS sessions underwent implantation of auditory cortex electrodes. Targeting was based on blood oxygen level–dependent activation evoked by tinnitus-matched sound, using functional MR imaging–guided neuronavigation.


Thirty-seven percent of the patients responded to ACS with tonic stimulation. Of the 63% who were nonresponders, half benefited from burst stimulation. In total, 33% remained unaffected by the ACS. The average tinnitus reduction was 53% for the entire group. Burst stimulation was capable of suppressing tinnitus in more patients and was better than tonic stimulation, especially for noise-like tinnitus. For pure tone tinnitus, there were no differences between the 2 stimulation designs. The average pure tone tinnitus improvement was 71% versus 37% for noise-like tinnitus and 29% for a combination of both pure tone and noise-like tinnitus. Transcranial magnetic stimulation did not predict response to ACS, but in ACS responders, a correlation (r = 0.38) between the amount of TMS and ACS existed. A patient's sex, age, or tinnitus duration did not influence treatment outcome.


Intracranial ACS might become a valuable treatment option for severe intractable tinnitus. Better understanding of the pathophysiological mechanisms of tinnitus, predictive functional imaging tests, new stimulation designs, and other stimulation targets are needed to improve ACS results.

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Katrin Van Loock, Tomas Menovsky, Maurits H. Voormolen, Mark Plazier, Paul Parizel, Dirk De Ridder, Andrew I. R. Maas and Juha A. Hernesniemi

The authors report the successful removal of Onyx HD-500 from an aneurysm sac by means of ultrasonic aspiration. This 46-year-old woman presented with progressive spasms of her left arm and leg due to mass effect and compression on the right cerebral peduncle 5 years after endovascular treatment of an unruptured giant posterior communicating artery aneurysm with Onyx HD-500. No filling of the aneurysm was detected on angiography.

The patient underwent a right pterional craniotomy and the aneurysm was opened to remove the Onyx mass. However, contrary to expectations, the aneurysm was still patent, filling with blood between the Onyx mass and the aneurysm wall. Under temporary clipping of the carotid artery, the Onyx mass within the aneurysm was removed in a piecemeal fashion using an ultrasonic aspirator and the aneurysm was then successfully clipped. The patient experienced significant improvement of the spasm after surgery. Angiography showed complete occlusion of the posterior communicating artery aneurysm.

It is rarely necessary to remove embolization material such as Onyx HD-500, and little is known about the most appropriate surgical technique. This case report demonstrates that removal can be safely accomplished by means of ultrasonic aspiration.