If anything, this is one of the cases illustrating tremendous resilience of the human body can muster.
General Feldmarshall Mikhail Illarionovich Golenishev-Kutuzov has been wounded thrice in his career and, what is more curious, each time he was hit in the head. He received his first, and most serious wound on 8th August 1774 (all dates according to Gregorian calendar) during the fight in the vicinity of the village Shumy (now Kutuzovka), close to the town of Alushta, when a rifle bullet pierced his skull. Then, on 18th August 1788, during the siege of Ochakov, he was struck again by a bullet in the cheek. Last, and the least dangerous incident occurred on 2nd December 1805 during the battle of Austerlitz, when Kutuzov was again hit in the cheek by a small piece of shrapnel. This was most likely a minor injury, however, and Kutuzov refused to leave battlefield to be treated stating that this is an insignificant wound.
The first and most dangerous wound was a bullet through-and-through wound that entered somewhere in the upper part of the left temple and exited through the right temple, close to the right supraorbital ridge. Given that the wound did not caused vision problems in the left eye and only resulted in ptosis (drooping of the lid) and reported strabismus of the right eye it is very possible that the bullet traversed the skull above the eyes, most likely damaging right orbicularis oculi (circular eye muscle), superior oblique muscle and trochlear nerve. On the other hand this also mean that the bullet had to traverse the cranial cavity, damaging the brain. We cannot however exclude the possibility that the bullet ricocheted from the inside of the frontal part of the skull, changing its trajectory. Furthermore, Kutuzov was hit when he entered the trench located below the enemy positions and thus was hit from the above, making it possible that even though the exit wound was located relatively low, the bullet could have passed close to the skull surface, damaging the meninges and grazing the brain. Nevertheless, it is almost certain that such injury must have caused at least some damage to the frontal lobe and prefrontal cortex. And there are reasons to think that this was exactly the case.
After the recovery that was described as nothing short of a miracle, Kutuzov seemed to be experiencing frequent headaches, dizzyness and balance problems making him unable to dance, what can indicate chronic meningitis and cerebrospinal fluid leak, aggravated by a seepage during a long recovery time. It should be noted however that even brain damage could be alleviated over time by regeneration or re-routing due to relatively young age of the patient (Kutuzov was only 29 at the time and was known to be very healthy).
According to both Alexander I, Kutuzov was known for his sexual apetite and the tzar himself was calling him 'a one-eyed satyr' while General Louis Alexandre Andrault de Langeron was apparently horrified of the Marshall's behavior, noting "He would consecrate his evenings to love, or at least his idea of love. These women, such as they were, held over him a most absolute and scandalous influence; [...] He cannot exist without having three to four women around him [...]".
While characterizing Kutuzov, Langeron notes that the former appeared to be conflicted, showing vastly different traits of character, to wit:
No-one had more spirit but less character than Kutuzov [...] A prodigious memory, great education, amiable disposition, pleasing and interesting conversation, good nature [...], such were Kutuzov’s charms. At the same time, violence, a boorish impropriety more suited to a peasant, especially in contacts with people of inferior status, rough simplicity [...] an overwhelming laziness and apathy, repulsive selfishness, a contemptible and disgusting libertinism, little discretion in financial matters. These were the flaws of this same man [...]
He was capable of distinguishing good and bad advice. Knew his way in a discussion. Understood what the best course of action is, but all of this was paralyzed by indecision, an apathy in mind and body [...] During battles he would not move, not unlike a living statue, except to cross himself when he heard the whistle of a nearby bullet. He never ventured or even wasn't unable to change anything including dislocation of the troops. He never personally supervised reconnaissance, never investigated positions of enemy or his own troops [...] Large and fat, he could not sit in the saddle for long and was fatigued quickly [...] This same indolence poisoned his administrative duties: he had had to force himself to pick up the pen. His subordinates, deputies, and secretaries manipulated him freely and whilst he was undoubtedly more intelligent and better educated than them, he was unable to review and their work, not to mention supervise or direct it.
These passages are of particular interest, because they point out several traits that form a curious yet consistent clinical image. Emotional outbursts and asocial behaviour related to the diminished consideration of consequences (are axial symptoms of pre-frontal cortex damage, while hypersexuality, overeating, diminished response to fear and apathy are typical for the Klüver–Bucy syndrome resulting from lesions of temporal lobe. The prevalence of the former is consistent with the damage, as the bullet traversed the pre-frontal gyrus while only slightly and unilaterally damaging the left temporal lobe.
It should also be noted that Jean Joseph Massot, a physician in the employ of Russian monarch and assigned to the troops taking part in the Crimean theatre of war in mid-1780s (he tended to Kutuzov after he was shot during the siege of Ochakov), although very young, had an extensive knowledge concerning head wounds. He noted that this type of wounds is not uncommon among soldiers and although very dangerous and most often fatal, people are still known to recover even after suffering direct trauma to the cranium and resulting intracranial hemorrhage. He also made an observation that soldiers are not too unlikely to survive the shot itself and the removal of the bullet with apparently good prognosis, but they may still succumb to illness up to several days after the operation. Massot correctly assumed this is most likely caused by the combination of internal hemorrhage, exsanguination and increased pressure on cerebral structures that was impossible to alleviate with trepanning.
This indicates that it was not impossible, although still uncommon, to survive direct shot to the head. Furthermore, it is also possible that Kutuzov was shot by a Turkish marksman using not the heavy musket but rather a light hunting rifle, typically of much smaller caliber (I'm not an expert on Ottoman weapons, but contemporary German and Polish counterparts often sported caliber of .32 or .40). Small caliber could account for limited extent of damage and low velocity of the bullets meant much lower hydrostatic shock in soft tissue in comparison to modern firearms) meaning that direct hit to the brain would not result in wide temporary channel and resulting wide and most likely fatal damage.
The second wound. suffered in 1788 is sometimes said to be almost identical to the first one, as described by prince Charles-Joseph von Ligne in his letter to Emperor Joseph II, although this is quite likely a result of confusion and is contradicted by memoirs of Kutuzov's grandson and notes of Massot who has treated Kutuzov and described the situation in the letter to Catherine II. According to the latter, the bullet entered the left cheek, damaged the mandible and some teeth in the upper jaw and exited through the back of the neck, missing all important blood vessels (interestingly, this damage seems to be quite similar to one suffered by Henry V at the battle of Shrewsbury in 1403, although Henry was struck with an arrow). This time, although it was still a shot to the head, Kutuzov recovered quickly but soon after he noticed that the physiological symptoms of the previous injury increased, quite possibly due to strain caused by the wound itself and significant exsanguination.
Summing it up, Kutuzov was wounded in the head three times, although only the first wound could have damaged the brain what led to psychosomatic problems Field Marshall continued to suffer until the end of his life and that were worsening with subsequent wounds and progressing age. Contemporary medical accounts allow us to assume, that that recovery from such injury, although unlikely, was by all means possible.
A.F. de Langeron, Mémoires de Langeron, Général d’Infanterie dans l’Armée russe, Campagnes de 1812, 1813, 1814, Paris 1902.
A.F. de Langeron, Записки графа Ланжерона. Война с Турцией 1806-1812 гг. [Notes of the Comte de Langeron. The war with Turkey 1806–1812] (Russian translation by E. Kamenskiy) in: Русская старина, 1908. vol. 134, no. 4., pp. 225-240.
F.M. Sinelnikov, Жизнь фельдмаршала Кутузова [Life of Field Marshall Kutuzov], Русская Симфония, 2007
N.A. Troitskiy, Фельдмаршал Кутузов. Мифы и факты [Field Marshall Kutuzov. Myths and Facts], Centrpoligraf, 2003