The act of maintaining balance requires the integrated function of the brain, spinal cord, peripheral nerves, the inner ear, and vision contributes as well. There is a rather large list of diseases that affect these areas and cause imbalance, and the following is a survey of some of the more common causes.
Beginning in the feet, certain types of nerve fibers are responsible for proprioception, knowing where the feet are in relation to the rest of the body, and also gauging how much weight the feet are supporting. If these nerve fibers are damaged it is called a peripheral neuropathy, and this is a common cause of balance impairment. Usually, someone with balance impairment due to peripheral neuropathy will also have other symptoms, such as tingling or pain in their feet, which may extend up their legs and eventually affect their hands as well. There are additionally many different types and causes of neuropathy.
The nerves in the arms, legs and trunk coalesce to form the spinal cord, and any number of conditions that affect the spinal cord can cause imbalance as well. The most common of these conditions is one of the disks between the vertebrae bulging out and compressing the spinal cord. This can usually be treated surgically. Additional diseases that can affect the spinal cord include multiple sclerosis, syringomyelia, vitamin B12 deficiency, myelitis, and many others. A detailed neurologic examination can generally reveal if the problem is located in the spinal cord or peripheral nerves, and this can be confirmed with MRI or nerve conduction studies.
Many diseases of the brain, and impairments in many different parts of the brain, can cause balance impairment. Just above the spinal cord, in a structure called the brainstem, a small collection of brain cells called the substantia nigra can get damaged and cause Parkinson's disease, another common cause of imbalance. Parkinson's has distinct features on the neurologic examination also, including tremor, stiffness, and slowness, and an experienced neurologist can diagnose it with 97% accuracy based solely on examining the patient.
Just behind the brainstem is the cerebellum, a large structure at the back and bottom of the brain which is involved in both balance and coordination. When this structure is damaged, and especially the central part, people have to walk with their feet wide apart to maintain balance. The most common source of damage to the cerebellum is chronic alcohol abuse, though many other diseases can affect this structure as well. The neurologic examination is also highly reliable in determining if there is impairment in the cerebellum, and this is usually confirmed with an MRI of the brain.
If the fluid filled cavities in the brain get enlarged, a condition termed hydrocephalus, this can also cause imbalance, and when this happens it is often associated with headaches and nausea. However, this cause of imbalance is hard to recognize on neurologic examination alone.
The inner ear is also involved in balance, and if one of the nerves in the inner ear gets inflamed, it will initially produce vertigo, an illusion of ongoing movement, but it is also common to have balance impairment once the vertigo has resolved due to residual damage to the nerve.
There are numerous other causes of imbalance, including for example stroke, multiple sclerosis, cervicogenic dizziness, and exotic conditions such as orthostatic tremor, and it can be quite helpful to see a neurologist with interest and expertise in balance disorders to determine the underlying cause.
