Thus, it has been suggested that free radicals, oxidative stress, and reactive oxygen species may play some role in the neuropathology of LNS.However, some evidence suggests against a role for uric acid in the neuropathology of Lesch–Nyhan syndrome:

Hyperuricemia associated with classic primary gout, which is caused by low uric acid renal clearance rather than uric acid overproduction, is not associated with neuropathology. Hypouricemia occurs in a number of purine disorders, in particular xanthinuria. Despite having complete absence of blood uric acid, xanthinuria patients do not have any neuropathology, nor any other disease states – other than the kidney stones caused by accumulation of insoluble xanthine in lieu of uric acid.Similarly,  uric acid does not penetrate the blood–brain barrier well. However, oxidative stress due to uric acid is now thought to figure in metabolic syndrome, atherosclerosis, and stroke, all syndromes associated with high uric acid levels. Similarly, Superoxide dismutase ( "SOD" ) and SOD-mimetics such as TEMPOL ameliorate the effects of hyperuricemia. Likewise, 6-hydroxydopamine (the putative animal model for Lesch–Nyhans neuropathy) apparently acts as a neurotoxin by generation of reactive oxygen species. It may be that oxidative stress induced by some other oxypurine such as xanthine causes the disease. Diagnosis
When an affected individual has fully developed the three clinical elements of uric acid overproduction, neurologic dysfunction, and cognitive and behavioral disturbances, diagnosis of LNS is easily made. Diagnosis is less easy in the early stages, when the three features are not yet obvious.
Such crystals deposited in joints later in the disease may produce gout-like arthritis, with swelling and tenderness. The overproduction of uric acid is present at birth, but may not be recognized by routine clinical laboratory testing methods. The serum uric acid concentration is often normal, as the excess purines are promptly eliminated in the urine. The crystals usually appear as an orange grainy material, or they may coalesce to form either multiple tiny stones or distinct large stones that are difficult to pass. The stones, or calculi, usually cause hematuria (blood in the urine) and increase the risk of urinary tract infection. Some affected people have kidney damage due to such kidney stones. Stones may be the presenting feature of the disease, but can go undetected for months or even years. Nervous system impairment
The periods before and surrounding birth are typically normal in individuals with LNS. The most common presenting features are abnormally decreased muscle tone (hypotonia) and developmental delay, which are evident by three to six months of age. Affected individuals are late in sitting up, while most never crawl or walk. Lack of speech is also a very common trait associated with LNS.Irritability is most often noticed along with the first signs of nervous system impairment. Within the first few years of life, extrapyramidal involvement causes abnormal involuntary muscle contractions such as loss of motor control (dystonia), writhing motions (choreoathetosis), and arching of the spine (opisthotonus). Signs of pyramidal system involvement, including spasticity, overactive reflexes (hyperreflexia) and extensor plantar reflexes, also occur.