Midbrain Lesion Bridges Akinetic and Cerebellar Mutism: A Case Report

Highlights

• A 10-year-old patient developed mutism and akinesia after a midbrain ischemic lesion following craniopharyngioma surgery, displaying features overlapping with akinetic mutism (AM) and postoperative pediatric cerebellar mutism syndrome (ppCMS).

• The case illustrates that AM and ppCMS may lie on a clinical spectrum driven by disruption of intersecting neurocircuits at the midbrain level.

• Treatment with methylphenidate led to gradual recovery of speech and motor function over 4 months, suggesting a potential therapeutic avenue for acquired mutism of midbrain origin.

• Acquired mutism can present with combined features of akinetic mutism and cerebellar mutism syndrome after midbrain injury.

• The midbrain is a convergence point for fronto-subcortical and cerebello-cerebral circuits involved in motivation and motor control.

• Methylphenidate may be beneficial in patients with midbrain-related mutism, but evidence remains limited to isolated cases.

Background

Mutism, the inability to produce speech, can result from diverse neuropathological processes. Among the recognized subtypes are akinetic mutism (AM), typically associated with bilateral fronto-subcortical pathway damage, and postoperative pediatric cerebellar mutism syndrome (ppCMS), which follows disruption of cerebello-cerebral circuits after posterior fossa tumor resection. AM is characterized by loss of speech and spontaneous motor activity (akinesia) despite preserved alertness, while ppCMS often presents with emotional lability and a delayed onset after surgery. Although the two syndromes have been considered distinct clinical entities, overlapping features have occasionally been reported, raising questions about shared underlying neurocircuitry.

Case Presentation

Obdeijn and colleagues report the case of a 10-year-old child who underwent surgical resection of a suprasellar craniopharyngioma. The postoperative course was complicated by a focal ischemic lesion in the midbrain. On postoperative day 5, the patient began to exhibit progressive loss of speech and voluntary motor function. By day 12, the child had become completely mute and akinetic, with no spontaneous movements. There was no spontaneous recovery. Two weeks after symptom onset, treatment with methylphenidate was initiated. The patient subsequently showed gradual improvement, regaining speech and demonstrating continued recovery of motor deficits up to 4 months after the ischemic event.

Discussion: Overlap Between Akinetic and Cerebellar Mutism

The authors highlight that this case exhibits clinical features of both AM (akinesia, mutism) and ppCMS (delayed onset, emotional lability, history of tumor surgery). The presence of a midbrain lesion in this patient suggests that the neurocircuits implicated in AM and ppCMS intersect at the midbrain level. The fronto-subcortical circuits subserving motivation and initiation of motor activity (including speech) pass through the midbrain, as do cerebello-cerebral connections involved in motor coordination and possibly speech initiation. Disruption at this junction could thus produce a mixed syndrome. The authors hypothesize that AM and ppCMS may represent a disease spectrum rather than fully separate disorders, with the midbrain acting as a critical node.

Expert Commentary

This case adds to a growing body of evidence that acquired mutism syndromes are not always easily categorizable. The observation of overlapping features in a single patient with a focal midbrain lesion provides anatomic insight into how damage at this location can affect multiple circuits simultaneously. However, it is important to note that this is a single case report; the response to methylphenidate, while encouraging, cannot be generalized without larger studies. The mechanisms by which methylphenidate—a dopamine and norepinephrine reuptake inhibitor—improves mutism in this context remain speculative. It may enhance fronto-subcortical motivation pathways or modulate cerebellar-thalamic signaling. Clinicians encountering post-surgical mutism should consider the possibility of a shared neurocircuitry disruption, particularly when a midbrain insult is present. Future research should aim to delineate the specific tracts involved using advanced neuroimaging and explore targeted pharmacologic interventions.

Clinical Implications

• When assessing postoperative mutism, clinicians should evaluate for both akinetic and cerebellar features, as a mixed presentation may point to midbrain involvement.

• Early pharmacologic intervention with agents such as methylphenidate may be considered, although evidence is limited and treatment should be individualized.

• Neuroimaging focusing on the midbrain and its connections (e.g., diffusion tensor imaging) may help clarify the underlying circuit disruption and guide prognostic counseling.

Conclusion

This case illustrates that a focal midbrain lesion can produce a mutism syndrome blending features of akinetic and cerebellar mutism, supporting the hypothesis that these conditions exist on a neurocircuitry continuum. The favorable response to methylphenidate warrants further investigation. For now, the findings underscore the importance of considering midbrain pathology in the differential diagnosis of acquired mutism and highlight the need for more precise circuit-based treatment strategies.

References

1. Obdeijn IV, Langereis EJ, Berk MC, Partanen M, Hoving EW, Brandsma R. Bridging the Gap: Neurocircuitry Behind Mutism: Insights From a Midbrain Lesion. Neurology. 2026-07-27;107(4):e218069. PMID: 42507976.