Spinal nerve involvement in early Guillain-Barré syndrome: The Haymaker and Kernohan's legacy.

Pathological studies of early Guillain-Barré syndrome (GBS), defined as of 10days of disease onset, are scanty making it difficult to interpret the physiopathology of clinical and electrophysiological features. In 1949, Webb Haymaker and James Kernohan reported 50 clinico-pathological studies of fatal GBS cases, 32 of them having died between days 2 and 10 after onset. They established that the brunt of initial lesions, consisting of endoneurial oedema interpreted as degenerative, relied on spinal nerves. That this oedema was inflammatory was soon thereafter recognized. Two decades later, however, the pathogenic role of endoneurial oedema was disputed. In experimental allergic neuritis, considered an animal model of GBS, the initial lesion appearing on day 4 post-inoculation is marked inflammatory oedema in the sciatic nerve and lumbosacral nerve roots. Additional detailed clinico-pathological studies corroborated that the appearance of epi-perineurium at the subarachnoid angle, where anterior and posterior roots join to form the spinal nerve, is a pathological hotspot in early GBS, there developing inflammatory oedema, incipient demyelination and endoneurial ischemic zones with axonal degeneration. Furthermore, nerve ultrasonography has demonstrated predominant spinal nerve changes in early GBS, either demyelinating or axonal. Other outstanding Haymaker and Kernohan's contributions were to clarify the complex nosology of the syndrome bringing under the same rubric Landry's paralysis, acute febrile polyneuritis and GBS, and critically analyzing GBS exclusion criteria by then prevailing. It is concluded that the authors' legacy remains as relevant as ever.