Current ALS treatments are limited by a focus on symptom management and lack of understanding of the disease’s cause, but new technologies like 3D printing can offer exciting opportunities for innovation, such as custom prosthetics, artificial muscles, tissue engineering, and personalized medicine, which could significantly improve patient outcomes.
Parkinson’s disease is the second most common neurodegenerative disease with 90,000 Americans being diagnosed every year. Parkinson’s is a difficult disease to detect; there are no blood or lab test to diagnosis it. Diagnoses are symptom based. Parkinson’s patients often do not know they have the disease until after having dealt with it for years. Some of the early symptoms such as facial masking (lack of facial expression), small handwriting, or speaking softly do not directly point to a Parkinson’s disease diagnoses. A patient comes in with tremors, muscle rigidity, poor balance, and slowed movements and are then assumed to have Parkinson’s disease. If their symptoms improve with medication, the diagnosis is confirmed. Biomechanics is a useful tool in the evaluation of the progression of the disease as well as its continued treatment.
The human brain is an organ that scientists are always interested in due to its complexity. Insight on how to treat and/or cure physiological illnesses in the brain, such as Alzheimer’s disease or a stroke, could significantly improve the overall wellbeing of society. A new research area called brain lymphatic drainage has been able to demonstrate potential innovative therapeutic strategies to address these neurological diseases. A critical investigation of the brain biology along with biofluid flow by engineers has opened the door to another impressive brain process!
General overview of fluid movement in lymphatic system. Figure obtained from Hong et al. 2014.
Humans have a lymphatic system in their body which is a system of lymphatic vessels that collect waste and other leaking fluids from blood vessels which helps maintain fluid levels in tissues. The lymphatic vessels deliver this fluid to lymph nodes, which are small organs containing immune cells, that filters and drains the fluid back to the blood.
The brain doesn’t contain lymphatic vessels and it was unclear how it drains its waste. However, many scientists and engineers have recently discovered that there are indeed components of a drainage system in the brain which is connected to the body’s lymphatic system. The interstitial fluid (fluid surrounding the cells within the brain that contain solutes; ISF) is sent to be mixed with cerebrospinal fluid (fluid between the brain and an outer dense tissue; CSF). This mixed CSF fluid is then drained into lymphatic nodes and is eventually returned to the lymphatic system. The collection and drainage of ISF or CSF can be done with multiple pathways (i.e., through outer tissue of brain, sponge-like bone near olfactory nerves, etc.). The figure below shows a simplified diagram of some brain lymphatic drainage pathways towards the lymphatic system.
Diagram of brain lymphatic drainage pathways that lead to cervical lymph nodes. Adapted from Sun et al. , 2018. Created with BioRender.com.
Fluid Dynamics in Brain Lymphatic Drainage
Fluid dynamics is the study of fluids in motion. In the proposed brain lymphatic drainage system, there is an exchange of ISF and CSF in fluid-filled compartments that surround the brain which is a vital process for maintaining a healthy brain. Thus, fluid dynamics can be used to describe the forces involved in driving this ISF-CSF exchange and its impact for brain health.
The pulsing of the blood vessel wall impacts the flow of CSF and thus impacts mixing with ISF. PVS in the diagram is the fluid-filled compartments mentioned and astrocytes are a type of brain nerve cell. Figure obtained from Rasmussen et al., 2022.
In a recent study, a group of scientists and engineers quantitatively investigated the flow of CSF in these fluid-filled compartments and identified it as a pulsatile flow (i.e., rhythmic and intermittent movement of fluid) driven by pressure changes within the heart. The above demonstrates how CSF flow is impacted. The authors then saw that an increase in overall blood pressure leads to a reduction of forward flow of CSF which can partly limit the ISF-CSF exchange and lead to accumulation of unwanted molecules in the brain. They stated that this would explain the previously identified correlation of hypertension and accumulation of peptides that are found in patients with Alzheimer’s.
As medicine progresses, the quality of life improves for everyone, resulting in more people living longer. Unfortunately, as a result of an increasing number of people living longer, the number of stroke victims has increased as well. A stroke is a disease that affects blood flow to and inside the brain, causing the loss of movement and control in parts of the body. This loss of control leaves stroke victims very dependent on relying on others to help live a normal life.
In the rapidly evolving modern world, technological advancements are allowing for more effective research and treatment of diseases, disorders, and injuries sustained by humans. One of the foremost areas of current research in the biomechanics field is that of its role in treatment and rehabilitation of neurological disorders such as amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). According to the United Nations, as many as 1 billion people in the world live with neurological disorders. This post will focus mainly on how biomechanics can aid in the treatment and rehabilitation of ALS and MS.
