Abstract:
A brief summary is presented of the life of Johann Friedrich Horner, the eminent Swiss
ophthalmologist, renowned for describing the effects of paralysis of the human cervical
sympathetic nerves. His early education, the quality of his professional training, and the
influence of his mentors, notably Carl Ludwig and Albrecht von Graefe, contributed to his
discovery of the syndrome. The full text of Horner’s original work (translated by J. F. Fulton,
1929a, Arch. Surg. 18:2025–2039) is cited. The history of clinical and experimental work
carried out on the autonomic nervous system prior to Horner’s discovery is reviewed, including
the studies of Pourfour du Petit (cited in Fulton, 1929a and Singer and Underwood, 1962,
Clarendon); Hare, 1838, Lond. Med. Gaz. 23:16–18; Bernard (cited by Singer and Underwood);
Budge (1853, Acad. de Sci., p.377–378); Mitchell et al. (1864, Lippincott). Hare and
Mitchell et al. came close to making the discovery but were apparently hindered by their
inability to interpret the signs they elicited in their patients. The experiments of Claude Bernard
gave succinct accounts of the effects of damage to the cervical sympathetic nerves in animals,
although there appears to be no evidence that he made similar observations in humans. Horner
was the first to give a detailed, scientifically supported account and accurately interpret the
signs of cervical sympathetic nerve damage in a human subject. The anatomy of the pathway is
reviewed and the detailed structure of its central part updated. Evidence from computerized
tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET),
and single-photon-emission computerized tomography (SPECT) studies have confirmed that
reciprocally connected centers in the insular cortex, central nucleus of amygdala, hypothalamus,
mesencephalic and pontine tegmentum, nucleus of tractus solitarius, and the ventrolateral
medulla form the central pathway. The nucleus of tractus solitarius is probably the main reflex
center for the sympathetic system, whereas the ventrolateral medulla serves as the pathway
through which the central neurons influence the preganglionic neurons of the thoracolumbar
outflow. Emotional and sensory inputs from the frontal and somatosensory cortices provide the
inputs needed by the insula to drive the sympathetic nervous system to produce appropriate
responses.
