The term "punch-drunk" has been known both among the public and the medical professionals for almost 100 years and has largely been associated with the mumbling speech, gait and personality changes of a retired boxer. In recent years the same patterns have been observed in athletes from other fields such as American football, ice hockey and wrestling, as well as in military personal. Chronic traumatic encephalopathy (CTE) refers to the underlying neuropathology associated with repetitive traumatic brain injury, while traumatic encephalopathy syndrome (TES) refers to the clinical syndrome associated with CTE. CTE is a neurodegenerative tauopathy which shows distinctive neuropathological patterns. Common macroscopic changes among individuals with repetitive TBI are cavum septum pellucidum, dilated ventricles, generalized brain atrophy and depigmentation of substanita nigra. Depositions of neurofibrillary tangles (NFTs) and TAR DNA-binding protein 43 (TDP-43) in specific brain regions are common microscopic observations. Individuals with TES often show signs of deterioration of neurological and cognitive function, with symptoms such as behavioral and mood changes, parkinsonian features, cognitive decline in memory and executive dysfunction, agitation and emotional dysregulation. The symptoms often present years after the received brain injuries with progressive deterioration. Several diagnostic criteria have been sought established for the diagnosis of both CTE and TES, with defining criteria for "definite", "probable", "possible" and "unlikely" CTE/TES based on medical history, clinical symptoms, biomarkers and neuropathological observations. As of today, the only possible way for a diagnosis of definite CTE is by autopsy. This review will attempt to give a broad view over the current understanding of the diagnosis by providing a literature research with emphasis on systematic review articles.