Chapter 5 covers the clinical part of the account left to us by the medical authors of the imperial period: the case histories, pathological descriptions and clinical narratives as they appear in Anonymus Parisinus, Aretaeus and Galen, as well as the medical developments in the following centuries, which will proceed very much along the lines traced by Galen. This is illustrated by the late-antique sources included in the last section of the chapter: Oribasius, Aetius, Alexander of Tralles and Paul of Aegina. The topics analysed include patient profiling and behaviours; the topic of ‘neighbouring diseases’ and ‘similar diseases’ to phrenitis (pleuritis and pneumonia, but especially lethargos as cold brain fever, symmetrical to the hot brain fever which is phrenitis); and the recurring symptoms. These form a clear picture by now, featuring fever, sensorial disturbance, cognitive damage, various ‘neurological’ signs like (notably) 'flocillation' (the compulsive picking of hair or flocks from one's clothes and blankets), sleep disturbance, voice alteration, expectoration, a certain quality of the urine and pulse, respiratory issues, and a rich and varied psychological disturbance, where hallucination stands out.

Chapter 4 moves to the medical texts of the imperial age, addressing first the theoretical approaches, under the subdivisions ‘localization’, semiotics, chronology and aetiology. The time frame involved here is the first to sixth centuries CE, with the main focus on Aretaeus and Galen. The two famous physicians offered strong accounts of phrenitis in terms of localization (with a centre towards the heart, first, and the brain, second), and also introduced sophisticated discussions about ‘sympathy’ and co-affection in the disease. They also addressed symptomatology and, in the case of Galen especially, took phrenitis as exemplary case for semiotic discussions and the exploration of causes.