Balance disorder in the context of Equilibrioception

Hyponatremia or hyponatraemia is a low concentration of sodium in the blood. It is generally defined as a sodium concentration of less than 135 mmol/L (135 mEq/L), with severe hyponatremia being below 120 mEq/L. Symptoms can be absent, mild or severe. Mild symptoms include a decreased ability to think, headaches, nausea, and poor balance. Severe symptoms include confusion, seizures, and coma; death can ensue.

The causes of hyponatremia are typically classified by a person's body fluid status into low volume, normal volume, or high volume. Low volume hyponatremia can occur from diarrhea, vomiting, diuretics, and sweating. Normal volume hyponatremia is divided into cases with dilute urine and concentrated urine. Cases in which the urine is dilute include adrenal insufficiency, hypothyroidism, and drinking too much water or too much beer. Cases in which the urine is concentrated include syndrome of inappropriate antidiuretic hormone secretion (SIADH). High volume hyponatremia can occur from heart failure, liver failure, and kidney failure. Conditions that can lead to falsely low sodium measurements include high blood protein levels such as in multiple myeloma, high blood fat levels, and high blood sugar.

Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.

Dizziness is a common medical complaint, affecting 20–30% of persons. Dizziness is broken down into four main subtypes: vertigo (~25–50%), disequilibrium (less than ~15%), presyncope (less than ~15%), and nonspecific dizziness (~10%).

Parkinsonism is a clinical syndrome characterized by tremor, bradykinesia (slowed movements), rigidity, and postural instability.

Both hypokinetic features (bradykinesia and akinesia) and hyperkinetic features (cogwheel rigidity and tremors at rest) are displayed in parkinsonism. These are the four motor signs that are found in Parkinson's disease (PD) – after which Parkinsonism is named – and in dementia with Lewy bodies (DLB), Parkinson's disease dementia (PDD), and many other conditions.

Progressive supranuclear palsy (PSP) is a non late-onset neurodegenerative disease involving the gradual deterioration and death of specific volumes of the brain, linked to 4-repeat tau pathology. The condition leads to symptoms including loss of balance, slowing of movement, difficulty moving the eyes, and cognitive impairment. PSP may be mistaken for other types of neurodegeneration such as Parkinson's disease, frontotemporal dementia and Alzheimer's disease. It is the second most common tauopathy behind Alzheimer's disease. The cause of the condition is uncertain, but involves the accumulation of tau protein within the brain. Medications such as levodopa and amantadine may be useful in some cases.

PSP was first officially described by Richardson, Steele, and Olszewski in 1963 as a form of progressive parkinsonism. However, the earliest known case presenting clinical features consistent with PSP, along with pathological confirmation, was reported in France in 1951. Originally thought to be a more general type of atypical parkinsonism, PSP is now linked to distinct clinical phenotypes including PSP-Richardson's syndrome (PSP-RS), which is the most common sub-type of the disease. As PSP advances to a fully symptomatic stage, many PSP subtypes eventually exhibit the clinical characteristics of PSP-RS.