On 2017 Nov 15, David Keller commented:

Does tunneling through brain parenchyma to implant DBS leads cause subtle verbal impairment?

In 2013, the following letter to the editor of the NEJM questioned the lack of significant loss of verbal fluency reported in EARLYSTIM, in contrast to that seen in prior trials.[1]

The investigators in the Controlled Trial of Deep Brain Stimulation in Early Patients with Parkinson's Disease (EARLYSTIM) found that “no significant between-group differences were observed for cognitive assessments” when they compared patients who received subthalamic neurostimulation for Parkinson's disease with those who received medical therapy alone. In a recent review, [2] Okun described a meta-analysis finding that “the most common cognitive side effect of deep-brain stimulation was a decrement in verbal fluency.[3] Impaired verbal fluency is characterized by communication difficulties and by problems in generating word lists.” Okun and colleagues also conducted a study that showed that a “decrease in verbal fluency is an effect of surgical electrode implantation, not an effect of stimulation.”[4]

Did the EARLYSTIM investigators use a technique of lead placement that avoided impairing verbal fluency, or were the tests they used for assessing cognitive outcomes not sensitive instruments for measuring verbal fluency?

References 1) Keller DL. Neurostimulation for Parkinson's disease with early motor complications. N Engl J Med. 2013 May 23;368(21):2037-8. doi:10.1056/NEJMc1303485#SA2. PubMed PMID: 23697522. 2) Okun MS. Deep-brain stimulation for Parkinson's disease. N Engl J Med 2012;367:1529-1538 3) Parsons TD, Rogers SA, Braaten AJ, Woods SP, Troster AI. Cognitive sequelae of subthalamic nucleus deep brain stimulation in Parkinson's disease: a meta-analysis. Lancet Neurol 2006;5:578-588 4) Okun MS, Gallo BV, et al. Subthalamic deep brain stimulation with a constant-current device in Parkinson's disease: an open-label randomised controlled trial. Lancet Neurol 2012;11:140-149

The EARLYSTIM investigators replied as follows:

Keller raises questions regarding the effect of neurostimulation on verbal fluency shown in all controlled studies. We assume that verbal fluency is also significantly worse in patients in the neurostimulation group than in those in the control group in EARLYSTIM. Therefore, we have added a second protocol, EARLYSTIM-speech, to compare standardized speech recordings at baseline and at 24 months. This study will provide more information not only on the frequency and severity of changes of word fluency but also on the effect of these changes on communication in real life.

The EARLYSTIM-speech add-on study has not reported results yet, but a recent private communication from Günther Deuschl, M.D.-Ph.D., promised that results will be reported soon.

On 2017 Nov 15, David Keller commented:

Does tunneling through brain parenchyma to implant DBS leads cause subtle verbal impairment?

In 2013, the following letter to the editor of the NEJM questioned the lack of significant loss of verbal fluency reported in EARLYSTIM, in contrast to that seen in prior trials.[1]

The investigators in the Controlled Trial of Deep Brain Stimulation in Early Patients with Parkinson's Disease (EARLYSTIM) found that “no significant between-group differences were observed for cognitive assessments” when they compared patients who received subthalamic neurostimulation for Parkinson's disease with those who received medical therapy alone. In a recent review, [2] Okun described a meta-analysis finding that “the most common cognitive side effect of deep-brain stimulation was a decrement in verbal fluency.[3] Impaired verbal fluency is characterized by communication difficulties and by problems in generating word lists.” Okun and colleagues also conducted a study that showed that a “decrease in verbal fluency is an effect of surgical electrode implantation, not an effect of stimulation.”[4]

Did the EARLYSTIM investigators use a technique of lead placement that avoided impairing verbal fluency, or were the tests they used for assessing cognitive outcomes not sensitive instruments for measuring verbal fluency?

References 1) Keller DL. Neurostimulation for Parkinson's disease with early motor complications. N Engl J Med. 2013 May 23;368(21):2037-8. doi:10.1056/NEJMc1303485#SA2. PubMed PMID: 23697522. 2) Okun MS. Deep-brain stimulation for Parkinson's disease. N Engl J Med 2012;367:1529-1538 3) Parsons TD, Rogers SA, Braaten AJ, Woods SP, Troster AI. Cognitive sequelae of subthalamic nucleus deep brain stimulation in Parkinson's disease: a meta-analysis. Lancet Neurol 2006;5:578-588 4) Okun MS, Gallo BV, et al. Subthalamic deep brain stimulation with a constant-current device in Parkinson's disease: an open-label randomised controlled trial. Lancet Neurol 2012;11:140-149

The EARLYSTIM investigators replied as follows:

Keller raises questions regarding the effect of neurostimulation on verbal fluency shown in all controlled studies. We assume that verbal fluency is also significantly worse in patients in the neurostimulation group than in those in the control group in EARLYSTIM. Therefore, we have added a second protocol, EARLYSTIM-speech, to compare standardized speech recordings at baseline and at 24 months. This study will provide more information not only on the frequency and severity of changes of word fluency but also on the effect of these changes on communication in real life.

The EARLYSTIM-speech add-on study has not reported results yet, but a recent private communication from Günther Deuschl, M.D.-Ph.D., promised that results will be reported soon.