Cerebellar stimulation: A hypothetical therapeutic model for substance use disorders.

Sir,

Substance use disorders (SUDs) hold a special position in psychiatry because their neurobiological and behavioral bases may be considered one of the best understood of all psychiatric disorders. Yet they can be frustrating to manage with a not so promising prognosis.[1] Recently, brain stimulation techniques such as deep brain stimulation (DBS) and repetitive transcranial magnetic stimulation (rTMS) are increasingly considered a panacea for various neuropsychiatric disorders. Advances in neurobiological understanding, neuroimaging, and targeted neuromodulation techniques are allowing us to stimulate specific regions of interest in the brain with pinpoint precision. Recently, both methods have been tried for SUDs. DBS of nucleus accumbens and subthalamic nucleus have been found to have promising results.[2] Dorsolateral prefrontal cortex is the other brain region targeted with rTMS for alcohol and other SUDs.[3]

However, the cerebellum has never been targeted by brain stimulation researchers for SUDs despite its role in nonmotor functions involving emotion, affect, and cognition has been recognized.[4] It has been widely studied for its dysfunction associated with chronic alcohol abuse. Recently, its role in the development of dependence has been elucidated. It has a role not only in the neurobiological underpinning of dependence but also in its behavioral conditioning.[5] Surprisingly, early research conducted, almost three decades ago, on animal brains had shown that cerebellar stimulation may modulate the functions of brainstem reticular nuclei and regions in the limbic and autonomic system, including hypothalamus, ventral tegmental area, periaqueductal gray, hippocampus, and amygdala.[6] Furthermore, recently, cerebellar vermal theta burst stimulation using rTMS has been found to be a safe and well-tolerated option for modulating affect, emotion, and cognition in refractory schizophrenia.[7] Patients with refractory motor epilepsy have also benefited with superomedial cerebellar cortical stimulation.[8]

Based on the above observations, we can hypothesize that cerebellar stimulation in alcohol/substance dependence syndromes could result in beneficial effects in three major domains:

Limbic/paralimbic modulation leading to release of neurotransmitters including dopamine may help in reducing craving and increasing salience of stimuli other than alcohol/substance

Frontal lobe modulation could improve the negative effect associated with drug withdrawal states, thereby reducing relapses. Its effect on the emotional and cognitive aspects may help in reducing impulsivity and improving attention toward other rewarding stimuli and judgment

Superomedial cerebellar cortical stimulation could help in reducing the incidence of withdrawal seizures and delirium, thereby significantly reducing the morbidity and mortality during acute detoxification stages.

Cerebellar stimulation, per se, using DBS and rTMS is not a new entity in the field of neuropsychiatry. Its effectiveness and safety profile have been demonstrated earlier. We recommend its usability in SUDs based on the above theoretical construct, wherein it could potentially have a wide range of effects from acute detoxification to chronic relapse prevention. Patient profile, treatment aspects, and risks with concurrent substance use require elucidation. Centers with adequate resources should seriously consider the option.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.