The same survey described the most common triggers of brain fog to be fatigue (91%), lack of sleep (90%), prolonged standing (87%) and dehydration (86%).Neuropsychological testing has shown that a POTS patient has reduced attention (Ruff 2&7 speed and WAIS-III digits forward), short-term memory (WAIS-III digits back), cognitive processing speed (Symbol digits modalities test) and executive function (Stroop word color and trails B).A potential cause for brain fog is a decrease in cerebral blood flow (CBF), especially in upright position.There may be a loss of neurovascular coupling and reduced functional hyperemia in response to cognitive challenge under orthostatic stress – perhaps related to a loss of autoregulatory buffering of beat-by-beat fluctuations in arterial blood flow. Causes
The symptoms of POTS can be caused by several distinct pathophysiological mechanisms. These mechanisms are poorly understood, and can overlap, with many patients showing features of multiple POTS types. Many people with POTS exhibit low blood volume (hypovolemia), which can decrease the rate of blood flow to the heart. To compensate for low blood volume, the heart increases its cardiac output by beating faster, leading to the symptoms of presyncope and reflex tachycardia.In the 30% to 60% of cases classified as hyperadrenergic POTS, norepinephrine levels are elevated on standing, often due to hypovolemia or partial autonomic neuropathy. A smaller minority of people with POTS have (typically very high) standing norepinephrine levels that are elevated even in the absence of hypovolemia and autonomic neuropathy; this is classified as central hyperadrenergic POTS. The high norepinephrine levels contribute to symptoms of tachycardia.
Stimmler syndrome is a rare autosomal recessive congenital disorder first described by Stimmler et al. in 1970. It is characterized by dwarfism, diabetes, a small head, and high levels of alanine in the urine. Symptoms
Symptoms for the disease include microcephaly, a low birth weight, dwarfism, small teeth, and diabetes. The symptoms of Stimmler syndrome are closely related to a disease studied by Haworth et al. in 1967 as well as Leigh subacute necrotizing encephalopathy with lactic acidosis

Pathophysiology
Stimmler syndrome is an autosomal recessive genetic disorder whose symptoms appear before birth or during infancy. In a study of two sisters born within a year of each other, both with Stimmler syndrome, it was found that high levels of alanine, pyruvate, and lactate were present in both the blood and urine. It was believed that the alanine was derived from the pyruvate. Diagnosis
Treatment
References


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