Parkinson’s disease and tardive dyskinesia (TD) are two distinct neurological conditions that can exhibit overlapping symptoms, which can sometimes make it challenging to differentiate between them, especially when assessing individuals who have been suffering from the disease for a long time. It is not necessary for all known and common symptoms of the condition to overlap. However, there are glaring differences in terms of severity and how these problems can develop, affecting individuals.

Tremors
One of the most recognizable symptoms of Parkinson’s disease  and Tardive dyskinesia is early tremors. Resting tremors are a typical feature of Parkinson’s disease, affecting a majority of the patients. These tremors generally develop in the arms and legs. Second, if there is any activity, the tremors decrease or stop during purposeful movement. This means Parkinson’s tremors are typically rhythmic and worsen when the person is sitting or lying down. The tremors may initially be subtle, like a slight shaking of the hand, but can become more pronounced over time. Tardive dyskinesia also involves tremors that may more or less resemble the resting tremors observed in PD. However, TD tremors can be more irregular and jerkier, more prolonged, and visibly evident when compared to the subtle movements of Parkinson’s. A thorough diagnosis will be necessary to confirm the underlying trigger of such tremors.

Involuntary movements
While Parkinson’s primarily presents with bradykinesia (slowness of movement), it can also involve involuntary movements called dyskinesia. These movements are typically observed as sudden writhing or twisting motions of the limbs, the trunk, or even the face. TD mainly involves involuntary and repetitive movements of the face and mouth, among other affected body parts. These movements can sometimes resemble the dyskinesia symptoms seen in advanced stages of Parkinson’s disease. However, there are glaring differences that one cannot simply overlook. One of the characteristic signs of TD is the presence of involuntary facial movements. These include excessive and involuntary blinking of the eyes, repetitive or uncontrolled puckering or smacking of the lips, and involuntary tongue protrusion or rolling, which can lead to chewing or lip biting, and facial grimaces or contortions, such as pulling of the mouth or facial muscles.

Facial and oral movements
Facial expressions may become less animated in Parkinson’s, and individuals may experience difficulty swallowing and speaking due to muscle stiffness. However, for TD, the disorder often presents with facial and oral movements, such as lip smacking, puckering, and grimacing, which can resemble some of the facial and oral symptoms seen in Parkinson’s. In tardive dyskinesia, the tongue may dart in and out of the mouth involuntarily. Further, the condition will manifest involuntary jaw movements, including clenching, grinding, or lateral shifting. Note that these symptoms are more or less overlapping, but there is a clear distinction factor.

Muscle rigidity
Muscle stiffness and rigidity are prominent features of Parkinson’s and can affect various muscle groups, contributing to a slow and shuffling gait. This greatly affects the balance of a person as well. Bradykinesia refers to slowness of movement and is another hallmark symptom of Parkinson’s disease. People with Parkinson’s may notice that tasks that were once easy and quick to accomplish, like buttoning a shirt or tying shoelaces, become increasingly challenging due to muscle stiffness and rigidity. Facial expressions may also become less animated, and the person may have difficulty initiating or executing movements. In TD cases, patients may not present with the same degree of generalized muscle rigidity seen in those affected with Parkinson’s, but it can lead to localized muscle stiffness, particularly in the facial and oral muscles. While TD primarily affects the face and mouth, it can also involve other body parts, such as the arms, legs, and trunk. In some cases, individuals with TD may exhibit repetitive and involuntary movements of their limbs, making it challenging to perform fine motor tasks.

Balance and gait disturbances
Postural instability and balance problems are common in Parkinson’s disease, leading to a stooped posture and an increased risk of falls. Balance and coordination problems, known as postural instability, can develop as Parkinson’s progresses. Individuals with Parkinson’s may have difficulty maintaining an upright posture and may be prone to falls. They may also experience changes in their gait, such as taking shorter and shuffling steps. While TD primarily affects involuntary movements, it may not directly impact balance and gait to the same extent as Parkinson’s. However, severe TD can lead to posture changes. TD can extend to the trunk and hips, leading to twisting or writhing movements of the torso. These movements may be less common than those affecting the face, but they can significantly impact a person’s posture and overall comfort.

Loss of smell (Hyposmia)
A diminished sense of smell, or hyposmia, can be an early sign of Parkinson’s disease. This loss of smell may occur years before motor symptoms become apparent. It can be subtle and often go unnoticed, but it is a potential indicator of the disease when combined with other symptoms. Loss of smell is not a prominent factor when it comes to tardive dyskinesia. However, it can be a point of concern for many patients who are not familiar with the symptom development of Parkinson’s as well. This is why tests need to be done to rule out any trigger factors that indicate conditions apart from Parkinson’s or tardive dyskinesia. The intensity of the symptoms will also vary accordingly.

It’s important to emphasize that a thorough clinical evaluation, including a comprehensive review of the individual’s health history, physical examination, and potentially imaging or other tests, is essential for accurate diagnosis and differentiation between Parkinson’s disease and TD. Additionally, consulting with a neurologist or movement disorder specialist can be particularly helpful in making a precise diagnosis and developing an appropriate treatment plan. Proper identification of the underlying condition is crucial to provide the most effective management and support for the individual’s specific needs.