Hyperacusis Brain Changes: MRI Review

A 2026 systematic review of 11 MRI studies provides the clearest picture yet of what happens inside the brain of someone with hyperacusis. Researchers Rania Alkahtani, Reem Elbeltagy, and colleagues from Princess Nourah bint Abdulrahman University analyzed structural, functional, and connectivity data, revealing a pattern of widespread neural alteration. The work, published in *Frontiers in Human Neuroscience*, moves past describing symptoms to identifying their biological roots.

**Methodology: Synthesizing Evidence from Three MRI Techniques**

The team conducted a systematic review to consolidate findings from studies using three main types of magnetic resonance imaging. Structural MRI (sMRI) measures brain anatomy, like grey matter volume. Functional MRI (fMRI) tracks blood flow changes to map brain activity during tasks or at rest. Diffusion Tensor Imaging (DTI) visualizes the white matter tracts that connect different brain regions.

They included 11 studies that met strict criteria, all comparing individuals with hyperacusis to control groups without sound sensitivity. By calculating standardized mean differences (SMDs)—a statistical measure of effect size—the researchers could quantify how substantial the brain changes were. An SMD above 0.8 is typically considered large; several findings in this review far exceeded that threshold. The analysis also accounted for high heterogeneity between studies, using sensitivity checks to ensure robust conclusions.

**Functional Hyperactivity in the Auditory Core**

The fMRI data presented the most consistent story. Individuals with hyperacusis showed significantly increased neural activity in core auditory processing centers. This includes Heschl’s gyrus, the brain’s primary auditory cortex, and the surrounding superior temporal gyrus.

Notably, the parahippocampal area, which sits at the crossroads of auditory processing and memory, also showed hyperactivity. The effect sizes for these activations were remarkably high, with SMDs frequently greater than 5.0. This indicates an exaggerated, amplified response to sound within the brain’s central hearing pathways. It’s a neural correlate of the perceptual experience: ordinary sounds are not processed as ordinary. For a deeper look at how brain responses differ between conditions, see our article on Brain Responses to Sounds: Misophonia vs Hyperacusis.

**Structural Changes in Sound Modulation Regions**

Where fMRI showed *overactivity*, structural MRI revealed *understructure*. The sMRI analysis identified a specific region with reduced grey matter volume: the right supplementary motor area (SMA). The effect size here was large (SMD = 2.10).

The SMA is not a primary auditory region. Its roles include motor planning and, critically, the prediction and modulation of sensory consequences. A compromised SMA could impair the brain’s ability to “gate” or filter incoming auditory signals, leaving the hyperactive auditory cortex unchecked. This structural finding points to a breakdown in the brain’s internal regulatory system for sound.

**Disrupted Connectivity in Auditory Pathways**

DTI findings completed the triad by showing that the communication lines themselves are altered. The review highlighted reduced integrity in key auditory pathways, including those involving the medial geniculate nucleus and the inferior colliculus. These are critical relay stations in the brainstem and thalamus that funnel sound information from the ear to the cortex.

Altered white matter in these pathways suggests inefficient or disrupted transmission of auditory signals. This disruption could contribute to the distorted processing seen in the cortical areas, creating a loop of dysfunction from the brainstem up. Similar investigations into neural connectivity changes are explored in related conditions, as discussed in Cerebral Blood Flow Changes in Tinnitus Explained.

**Practical Implications for Diagnosis and Care**

These converging results from multiple imaging modalities confirm that hyperacusis is not simply an ear problem or a psychological quirk. It is a whole-brain condition involving auditory, regulatory, and emotional networks. The parahippocampal activity, for instance, ties sound processing to memory and emotional centers, explaining the distress and aversion that characterizes the disorder.

This evidence directly supports a shift toward integrated, multidisciplinary care. Effective management likely requires a combination of approaches:
* **Neurological:** Therapies aimed at calming central auditory hyperactivity and potentially retraining sound modulation networks.
* **Psychological:** Addressing the conditioned emotional responses and anxiety that reinforce the neural patterns.
* **Perceptual:** Sound therapy and habituation exercises that must be designed with this altered brain state in mind.

The review’s authors explicitly call for diagnostic protocols that consider this multisystem view. Future treatments might target specific neural mechanisms, such as the engagement of the supplementary motor area’s regulatory function. Some emerging approaches focus on rewarding non-reactive brain states, a concept touched upon in our piece on Sensory-Sensitive Generative Music Rewards.

**Conclusion**

The systematic review by Alkahtani et al. provides a foundational brain map for hyperacusis. It shows a condition defined by amplified auditory cortex activity, weakened regulatory structure, and faulty neural connections. These measurable changes validate patient experiences and move the discussion firmly into the domain of neurobiology. Understanding hyperacusis as a complex brain disorder is the first, essential step toward developing more effective and targeted interventions.

**Source:** Alkahtani R, Elbeltagy R, Hamd ZY, Abdoelrahman Hassan AB. Structural and functional brain alterations in patients with hyperacusis: MRI systematic review. *Front Hum Neurosci*. 2026;20:1785826. doi:10.3389/fnhum.2026.1785826. PMID: 42022241.