Speech & DBS
Speech changes are a common symptom of Parkinson’s, tremor or dystonia. The cause is multifactorial and typically speech changes occur very slowly over time. (This distinction is important.) Speech can also be altered by deep brain stimulation and is one of the most common stimulation related side effects and great source of patient dissatisfaction. Almost all speech disturbances can be reversed if the speech change is related to stimulation.
Other causes of speech problems after DBS can occur from the surgery such as bleeding (stoke) or tissue damage. These complications are uncommon but are serious and may involve more than just speech, such as walking and thinking. Having a stoke from other causes (high cholesterol, high blood pressure) can also cause speech problems and are unrelated to DBS.
Speech changes can also occur from too low or too high medication dose, dyskinesia, tremor, fatigue and illness. The vocal cords can be a source of voice change but is typically noticed prior to DBS and should always be assessed by an ENT physician specialist. A change in speech can be a sign of a serious medical conditions.
Stimulation dose is not much different than medication dose. Too little dose – not enough benefit, too high dose – side effects occur. Stimulation and medication are similar in that there is a maximum benefit and always a risk of side effect if the dose is too high.
Useful Tips: The following are some tips that patients can use to assist their medical provider in troubleshooting speech problems after DBS.
- See a speech therapist for a computerized speech assessment – on medications. This is the benchmark for all future speech assessments after DBS.
- Optimize speech, posture and breathing for the best possible speech before surgery.
- Optimal speech depends on optimal medication if you have Parkinson’s.
- Make a recording of your speech to use later if needed to assess speech changes.
- Write down for you doctor when your speech was the best and when you first noticed a change. Some patients remember one appointment that resulted in speech slurring. I see some patients that tell me speech was good a couple years ago and then started to get worse. This could be disease progression or it could be from a gradual increase in stimulation intensity. The time-line will help determine what caused speech to change. Note how your speech changed, such as loss of volume, mumbling, stuttering or slurring. If you have a recording of your speech when it was good, bring it to your appointment.
How I assess speech changes in my patients after DBS:
- If the speech change occurs prior to turning on stimulation for the first time, I assess and monitor cognition. If the speech change is related to a change in verbal fluency (cognition), it may improve over a few months. Verbal fluency problems are related to finding the right word or completing sentences (language aspect of cognition) but commonly lumped into the speech category after DBS.
- If the speech change is after stimulation has been on, I set up an appointment to specifically assess speech. The patient should be On medications for the appointment. I use a simple assessment to establish a baseline by asking my patients to read the rainbow passage. I audio-record speech if the problem is complicated. I then turn off one side at a time. If speech improves with stimulation off, I adjust stimulation parameters to eliminate the speech problems. This is generally not difficult if the speech problem is from overstimulation.
- Almost always, the cause of the speech problem is too high stimulation intensity. This is a very reversible cause and reducing stimulation intensity can resolve almost all speech problems related to DBS. This assumes good placement of the electrodes in the brain. During DBS surgery, I talk with my patients to ensure speech is not being impacted to optimize electrode placement. (One very good reason to have DBS while awake)
- A common myth is that only the left side of the brain is involved in causing speech problems. This is not true. The left brain does control language for many people, but then so does the right brain in some. Language and speech are two very different functions controlled by very different areas of the brain.
- Tremor is one of the most common causes of pushing stimulation too high. I think this is most likely because we can see the tremor and tremor will increase with emotions and stress. Some patients and medical providers expect tremor to just stop instantly and if it doesn’t, stimulation intensity is increased until tremor stops, even when stimulation causes the leg to drag, the hand to cramp, speech to slur or balance problems. However, like with other symptoms, it takes time for stimulation to work. Over-stimulating will stop tremor quickly but will more than likely cause un-necessary speech problems and most importantly can also cause swallowing problems, falls and increased slowness and stiffness (like the tin-man). Having appropriate expectations for DBS and knowing the limits can help avoid stimulation side effects and symptoms that mimic disease progression.