The evolution of brain surgery on awake patients

In the early days of modern neurological surgery,
the inconveniences and potential dangers of general anesthesia
by chloroform and ether using the so-called “open-drop
technique” led to the quest for alternative methods of anesthesia.
Besides preventing the feared side effects, the introduction
of regional anesthesia revealed another decisive advantage
over general anesthesia in neurosurgery: While intraoperative
direct cortical stimulation under general anesthesia
could only delineate the motor area (by evocation of contralateral
muscular contraction), now, the awake patients were
able to report sensations elicited by this method. These properties
advanced regional anesthesia to the regimen of choice
for cranial surgeries in the first half of the 20th century. While
technical advances and new drugs led to a progressive return
to general anesthesia for neurosurgical procedures, the use of
regional anesthesia for epilepsy surgery has only decreased in
recent decades. Meanwhile, awake craniotomies regained
popularity in oncologically motivated surgeries, especially in
craniotomies for diffuse low-grade gliomas. Intraoperative
mapping of brain functions using electrical stimulation in
awake patients enables not only for increased tumor removal
while preserving the functional status of the patients but also
opens a window to cognitive neuroscience. Observations during
such interventions and their correlation with both pre −
and postoperative neuropsychological examinations and functional
neuroimaging is progressively leading to new insights
into the complex functional anatomy of the human brain.
Furthermore, it broadens our knowledge on cerebral network
reorganization in the presence of disease—with implications
for all disciplines of clinical neuroscience.