Sleep disturbance is common after head injury. Here is part of an article I wrote on posttraumatic sleep disturbance:
Patients with narcolepsy secondary to a head injury or posttraumatic hypersomnia often require stimulant medication such as methylphenidate or amphetamines in doses similar to those for idiopathic narcolepsy-cataplexy syndrome. Modafinil may be the medication of first intention; it has fewer side-effects overall than the other stimulants. The dosage is usually 300 to 400 mg, administered in 2 divided doses in the morning and at lunch time. Modafinil, however, activates hypothalamic regions and does not act directly through dopaminergic or noradrenergic pathways; and patients with severe head trauma who complain of intellectual slowness may benefit more from amphetamine-like medications. These medications will have a general “activating” effect that is not solely devoted to sleepiness. Of course, any coexistent sleep pathology or neurologic disease requires independent management. The potential beneficial effects of naps have not been studied; they should probably be restricted to less than 30 minutes to avoid significant sleep inertia effects. They should be taken when the patient feels sleepiest but not within 4 or 5 hours of habitual nocturnal sleep time.
Cases of sleep apnea resulting from a head injury are treated in the usual manner with continuous or bilevel positive airway pressure therapy. Sometimes the spontaneous/timed mode of bilevel positive airway pressure therapy is necessary for central sleep apnea and mixed obstructive/central sleep apnea. Adaptive-servo ventilation has recently become available to treat central and mixed sleep apnea, but experience in non-heart failure patients is limited. Treatment of sleep apnea should be conducted by a sleep disorders specialist. Posttraumatic organic insomnia has generally proven difficult to treat. Patients respond rather poorly to the benzodiazepine hypnotics employed to help initiate and maintain sleep. Cognitive behavioral therapy, including stimulus control, sleep restriction, cognitive restructuring, sleep hygiene education, and fatigue management, can improve nocturnal sleep quality as well as reduce daytime fatigue (Ouellet and Morin 2007
You can read more at Medlink Neurology