Neurosurgical Causes of Pulsatile Tinnitus

Neurosurgery 90:161–169, 2022

Traditionally in the domain of the otolaryngologist, pulsatile tinnitus (PT) has become increasingly relevant to neurosurgeons.

PT may prove to be a harbinger of life-threatening pathology; however, often, it is a marker of a more benign process.

Irrespectively, the neurosurgeon should be familiar with the many potential etiologies of this unique and challenging patient population.

In this review, we discuss the myriad causes of PT, categorized by pulse-phase rhythmicity.

Pulsatile versus non-pulsatile tinnitus in idiopathic intracranial hypertension

Acta Neurochirurgica (2018) 160:2025–2029

Tinnitus is a symptom commonly associated with idiopathic intracranial hypertension (IIH) that can have a profound effect on quality of life. We aim to determine tinnitus symptom response after dural venous sinus stenting (DVSS) or CSF diversion with a shunt, in patients with both pulsatile (PT) and non-pulsatile tinnitus (NPT).

Methods: Single-centre cohort of IIH patients (2006–2016) who underwent 24-h ICP monitoring (ICPM). An un-paired t test compared ICP and pulse amplitude (PA) values in IIH patients with PT vs. NPT.

Results: We identified 59 patients with IIH (56 F:3 M), mean age 32.5 ± 9.49 years, 14 of whom suffered from tinnitus. Of these 14, seven reported PT and seven reported NPT. Patients with tinnitus had a mean 24-h ICP and PA of 9.09 ± 5.25 mmHg and 6.05 ± 1.07 mmHg respectively. All 7 patients with PT showed symptom improvement or resolution after DVSS (n = 4), secondary DVSS (n=2) or shunting (n = 1). In contrast, of the 7 with NPT, only 1 improved post intervention (DVSS), despite 2 patients having shunts and 5 having DVSS.

Conclusions: NPT and PT were equally as common in our group of IIH patients. DVSS appears to be an effective management option for IIH patients with a clear history of pulsatile tinnitus. However, non-pulsatile tinnitus was more persistent and did not respond well to either DVSS or CSF diversion.

Microvascular decompression for tinnitus

J Neurosurg 126:1148–1157, 2017

The objective of this study was to examine operative outcomes in cases of microvascular decompression (MVD) of cranial nerve (CN) VIII for tinnitus through a critical review of the literature.

METHODS Forty-three English-language articles were gathered from PubMed and analyzed. In this review, two different case types were distinguished: 1) tinnitus-only symptomatology, which was defined as a patient with tinnitus with or without sensorineural hearing loss; and 2) mixed symptomatology, which was defined as tinnitus with symptoms of other CN dysfunction. This review reports outcomes of those with tinnitus-only symptoms.

RESULTS Forty-three tinnitus-only cases were found in the literature with a 60% positive outcome rate following MVD. Analysis revealed a 5-year cutoff of preoperative symptom duration before which a good outcome can be predicted with 78.6% sensitivity, and after which a poor outcome can be predicted with 80% specificity.

CONCLUSIONS As the 60% success rate is more promising than several other therapeutic options open to the chronic tinnitus sufferer, future research into this field is warranted.

Deep Brain Stimulation of Heschl Gyrus

Heschl

Neurosurgery 77:940–947, 2015

Tinnitus is a source of considerable morbidity, and neuromodulation has been shown to be a potential treatment option. However, the location of the primary auditory cortex within Heschl gyrus in the temporal operculum presents challenges for targeting and electrode implantation.

OBJECTIVE: To determine whether anatomic targeting with intraoperative verification using evoked potentials can be used to implant electrodes directly into the Heschl gyrus (HG).

METHODS: Nine patients undergoing stereo-electroencephalogram evaluation for epilepsy were enrolled. HG was directly targeted on volumetric magnetic resonance imaging, and framed stereotaxy was used to implant an electrode parallel to the axis of the gyrus by using an oblique anterolateral-posteromedial trajectory. Intraoperative evoked potentials from auditory stimuli were recorded from multiple electrode contacts. Postoperatively, stimulation of each electrode was performed and participants were asked to describe the percept. Audiometric analysis was performed for 2 participants during subthreshold stimulation.

RESULTS: Sounds presented to the contralateral and ipsilateral ears produced evoked potentials in HG electrodes in all participants intraoperatively. Stimulation produced a reproducible sensation of sound in all participants with perceived volume proportional to amplitude. Four participants reported distinct sounds when different electrodes were stimulated, with more medial contacts producing tones perceived as higher in pitch. Stimulation was not associated with adverse audiometric effects. There were no complications of electrode implantation.

CONCLUSION: Direct anatomic targeting with physiological verification can be used to implant electrodes directly into primary auditory cortex. If deep brain stimulation proves effective for intractable tinnitus, this technique may be useful to assist with electrode implantation.