Neurology India, Vol. 58, No. 3, May-June, 2010, pp. 503
The need for more evidence-based reporting in deep brain stimulation
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Date of Acceptance: 17-Jun-2010
Code Number: ni10134
Doshi and Bhargava provide an interesting report on the relation between deep brain stimulation of the subthalamic nucleus (STN) and hypersexuality  and conclude that "this is probably the first case report where manifestation of hypersexuality is a predominant behavioral side effect of successful STN stimulation." It is regrettable though that the authors while deducing important clinical conclusions from the localization of the contacts do not document the electrode localization and refer, as to their surgical intervention, solely to their previous published article.  The previous article  does not provide, however, the crucial specifics indispensable in the evaluation and understanding of the newly presented cases.  Furthermore, one wonders why no attempt was made (in the second patient) to change the localization of the stimulating contacts and the stimulating parameters. The question, if the observed hypersexuality was secondary to the specific position of the contacts or due to stimulation remains unanswered.
The "significant improvement" of motor function noted in the 2 patients could have been due to stimulation of the adjacent dorsal structures of the STN as reported by Godinho and colleagues,  rather than to the STN. It remains quite intriguing why hypersexuality, if related to STN stimulation, is not reported more frequently, given the myriad of deep brain stimulation (DBS) STN interventions. Since the aberrant behavior resolved abruptly in patient 1 without changing the stimulation settings and was controlled in the second patient with antipsychotic medications, the hypothesis of STN stimulation-induced hypersexuality seems even less tenable. Hypersexuality is a complex pathologic phenomenon as described by Poeck and Pilleri in their important study,  involving lesions in "basal ganglia and limbic midline structures" and usually encountered within the context of mania, which in the DBS literature is reported with substantia nigra rather than with STN stimulation. The precipitate attribution of highly specific functions to basal ganglia nuclei, such as the STN will lead solely to a clouding of our understanding as to the specific functionality of the tightly packed and complex basal ganglia network. The statement that "This is probably the first case report where manifestation of hypersexuality is a predominant behavioral side effect of successful STN stimulation" should therefore be made with due caution. The detailing of the surgical procedure in these 2 patients and a postoperative scan would have presumably shed light on this important matter.
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