Is a neuro-surgeon, whose practice mostly consists of spinal surgeries, the best choice to do emergency surgery on a patient with brain trauma?

No, while a neurosurgeon is highly knowledgeable and skilled in spinal surgeries, they may not be the best choice for emergency surgery on a patient with brain trauma. A more qualified doctor to perform this type of surgery would be a board-certified Neurocritical Care Surgeon (NCS). An NCS is trained specifically to manage critically ill neurologic patients with conditions such as cerebral hemorrhage, or traumatic brain injury. They are also experienced in performing surgical interventions used to treat these types of catastrophic events such as decompressive craniectomy or elective intracranial pressure monitoring. Furthermore, an NCS has extensive experience in managing acute neurological illness leading up to the critical event and aftercare management which includes long-term recovery and rehabilitation.
In short, though it can depend on the situation at hand, an NCS is usually better equipped when it comes to emergency brain trauma surgeries than a neurosurgeon due to their specialized training and expertise geared specifically towards caring for critically ill neurological patients compared to spinal surgery specialization alone.