Post-Traumatic and Post-Neurosurgical Hypersomnia

Rafael Pelayo

For children with post-traumatic and post-neurosurgical hypersomnia the best-fitting diagnosis within the International Classification of Sleep Disorders (ICSD) 2e is hypersomnia due to a medical condition.¹ By definition, excessive sleepiness is described as having a duration of more than 3 months, although it may be more pragmatic to make this clinical diagnosis earlier. References cited in the ICSD are more applicable for adults. There is no clear distinction made for post-traumatic hypersomnia in children. Children who suffer significant head injury frequently experience significant sleep disturbances, particularly when the injury is severe enough to result in major loss of consciousness. Nonetheless, sleep disturbances may follow minor trauma in which a brief loss of consciousness occurs. In all instances, sleep patterns after the injury vary notably from the pre-trauma sleep habits.

Closed-head trauma is the most common event resulting in post-traumatic hypersomnia. Similar symptoms may occur after neurosurgical procedures and other brain traumas. It appears that the cause is less important than the location. Symptomatically, there is a variable period of initial coma that evolves into a post-traumatic hypersomnolence and excessive daytime sleepiness with or without sleep attacks or unintentional sleep episodes. Nocturnal sleep may or may not be prolonged compared with the pre-injury period. When total sleep time within each 24-hour day is increased, the term ‘post-traumatic hypersomnia’ is fitting. Associated symptoms are typically due to daytime sleepiness (e.g., concentration difficulties, amnesia of recent events, fatigue, and occasional visual problems). Chronic headache and minor neurologic signs of traumatic brain injury may also be present.

Every year in the United States, 50 000 people die and more than 1.4 million seek medical care for traumatic brain injuries (TBI). Approximately 5.3 million Americans live with brain-injury-associated long-term disabilities, such as seizure disorders and cognitive and psychosocial impairments.² TBI is a leading cause of morbidity and mortality in children. Each year, almost half a million children seek emergency care because of head trauma. Fortunately, the majority of children (90%) suffer only from minor injuries. Nevertheless, 37 000 children require hospitalization, and up to 2685 children per year do not survive their sustained injuries.³ The CDC (Centers for Disease Control and Prevention in the United States) reports TBI-related death rates for the different age groups as follows: 5.7/100 000 (0–4 years), 3.1/100 000 (5–9 years), and 4.8/100 000 (10–14 years). This rate increases approximately fivefold (24.3/100 000) for patients between 15 and 19 years. Pediatric TBI is most commonly caused by falls and non-accidental injury in younger children, and road traffic accidents (as pedestrians or passengers) in older children and adolescents.⁴

Head trauma has been reported to increase the likelihood of sleep-disordered breathing.⁵ A polysomnogram may be necessary to exclude this etiology for the hypersomnia. The mechanism by which head trauma may result in sleep-disordered breathing is not clear. It is hypothesized that a whiplash type of injury may damage the pharyngeal nerves, which would alter some of the airway reflexes. Performing a polysomnogram may not be clinically possible in a child after a head injury. Empiric use of positive airway pressure (PAP) therapy should be used very cautiously since basilar skull fractures are a contraindication to PAP due to potential pneumocephaly.

Ideally, quantification of hypersomnia with a multiple sleep latency test, MSLT, may be helpful, especially to distinguish true sleepiness from fatigue or depression. However, in the presence of severe trauma, conducting and interpreting an MSLT may not be possible. The ICSD specifically states that a clinical complaint of excessive sleepiness is ‘far more important’ than a short sleep latency on an MSLT.¹

A key question asked by patients and family members when addressing post-traumatic or post-neurosurgical hypersomnia is how long will the condition last and will it spontaneously resolve with time. To evaluate the prevalence and natural history of sleepiness following traumatic brain injury, Watson and colleagues undertook a prospective cohort study of 514 young men and adolescents with traumatic brain injury (TBI). The TBI group was compared to 132 non-cranial trauma controls, and 102 trauma-free controls. Subjects were evaluated at 1 month and 1 year after injury. Sleepiness was measured subjectively with a self-administered questionnaire from which the following four questions were asked: (1) I am sleeping or dozing most of the time – day or night, (2) I sit around half-asleep, (3) I sleep or nap more during the day, and (4) I sleep longer during the night. At the 1-month time point more than half of the TBI subjects reported sleepiness (55%). Of interest, 41% of non-cranial trauma controls also reported sleepiness, as did only 3% of trauma-free controls. The TBI group was not only more likely to report being sleepy but the severity of the sleepiness was also greater since a greater percentage of subjects with TBI endorsed each of the four sleepiness items than did both the trauma controls and trauma-free controls at 1 month. One year following injury, 27% of TBI subjects, 23% of non-cranial trauma controls, and 1% of trauma-free controls reported sleepiness.²

In this study, patients with TBI were sleepier than non-cranial trauma controls at 1 month but not 1 year after injury. The cause of the residual sleepiness is unclear. One important factor in predicting persistent sleepiness is the severity of trauma. The brain injury of the majority of patients in this study was considered mild. To better understand the role of severity, the brain-injured subjects were divided into injury-severity groups based on time to follow commands (TFC) after the injury. The subgroup that was able to follow commands less than 24 hours after injury was less sleepy at the 1-month measurement than the 7- to 13-day and 14-day or longer TFC groups. At 1 year, the non-cranial trauma control group and the ≤24-hour TFC group were less sleepy than the 14-day or longer TFC group. Overall sleepiness improved in many patients in this study, with the TBI group more likely to improve than the non-cranial trauma group. Sleepiness improved in 84% to 100% of TBI patients as compared with 78% of the non-cranial trauma control group. However, about a quarter of TBI subjects remained sleepy 1 year after injury. In addition, patients with more severe brain injuries were unable to participate in the study and the authors felt this could have resulted in an underestimation of the true extent of sleepiness in the TBI group.²

It is of interest that significant and persistent hypersomnia was present in the non-brain trauma group even though the sleepiness was not as severe as the TBI group. No details about the type of trauma in the former group are provided.² This raises the question of what is the cause of the hypersomnia. We can speculate that perhaps adolescents’ and young adults’ whiplash-type injuries were included in the non-brain trauma group which, as mentioned above, can develop sleep-disordered breathing. Non-brain trauma victims may have poor sleep for other reasons that can lead to daytime hypersomnia. For example, chronic pain and insomnia may develop in this population.

Symptoms resulting from closed-head injury depend on the location of injury within sleep-regulating brain areas. Areas of the brain expected to be involved are those most commonly related to maintaining wakefulness, including but not limited to the brainstem reticular formation, posterior hypothalamus, and the region of the third ventricle. Shearing forces along the direction of main fiber pathways can lead to microhemorrhages in these areas. High cervical cord trauma has also been known to cause sleepiness and unintentional sleep episodes.6,7 Whiplash injury may result in hypersomnia, with consequent sleep-disordered breathing. In these cases, the hypersomnolence appears to be secondary to the respiratory abnormality.⁵ Countercoup injuries commonly occur at the base of the skull and may result in organic post-traumatic sleeplessness. These types of injury occur in areas of bony irregularities (especially the sphenoid ridges), with consequent damage to the inferior frontal and anterior temporal regions, including the basal forebrain.⁸ Injury to the posterolateral hypothalamus provides a potential physiologic explanation for post-injury sleepiness. Levels of hypocretin, an alerting neuropeptide, have been shown to be lower in patients with acute moderate to severe TBI.^9,10 Thus, trauma-induced transient reductions in hypocretin may be an unappreciated cause for hypersomnia. This would be consistent with case reports of post-traumatic narcolepsy and cataplexy.¹¹ Hypersomnia and insomnia are not the only sleep symptoms that can develop after a traumatic brain injury. Rodrigues and Silva have reported a patient with aggressive body movements during rapid eye movement (REM) sleep and periodic limb movements after a traumatic brain injury consistent with REM sleep-behavior disorder.¹²

A more recent multi-center prospective study was performed on sleep disturbances in children with TBI by Tham and colleagues.¹³ This study followed 729 children for 24 months following a TBI) and compared them to 197 children with orthopedic injury (OI), who served as controls. Sleep disturbance was assessed using only one question from a standardized questionnaire completed by the parents. Specifically, ‘How often did he/she have a problem with trouble sleeping in the last 4 weeks?’ Response options include ‘never’ = 0, ‘almost never’ = 1, ‘sometimes’ = 2, ‘often’ = 3, and ‘almost always’ = 4. Additional data were collected to determine functional outcomes in the areas of adaptive behavior skills and activity participation. Parental reports of pre-injury sleep disturbances were compared to reports of post-injury changes at 3, 12, and 24 months. The average age of the patients was 9 years. Both cohorts (children with TBI and OI) displayed increased sleep disturbances after injury. However, children with TBI experienced higher severity and more prolonged duration of sleep disturbances compared to children with OI. Risk factors for disturbed sleep included mild TBI, psychosocial problems, and frequent pain. Sleep disturbances emerged as significant predictors of poorer functional outcomes in children with moderate or severe TBI. The authors found that using a multivariate model with demographic and psychosocial factors, mild TBI was a significant predictive factor for sleep disturbances in their cohort. The authors proposed as an explanation that persons with mild TBI may have increased recognition of post-injury impairments, and therefore may be more likely to report sleep disturbances as an injury complication. In children with mild TBI, sleep disturbances may also be a symptom of increased awareness of post-injury changes subsequently reported by parents and caregivers. The other important predictors of sleep disturbances in the TBI cohort were frequent pain and the presence of psychosocial problems.

An important distinction between children and adults with TBI is that the neurosystem is maturing but not yet completely developed. The timing of the injury relative to the child’s age and maturation needs to be considered. Crowe and colleagues studied participants injured across various stages of childhood to examine the influence of age on recovery and see if it fits an early vulnerability or critical developmental periods model. A total of 181 children with TBI were categorized into 4 age-at-injury groups – infant, preschool, middle childhood, and late childhood – and were evaluated at least 2 years post-TBI with neurocognitive testing (IQ). The study found that overall, the middle childhood group had lower IQ scores across all domains. The authors concluded that contrary to expectations, children injured in middle childhood demonstrated the poorest outcomes which may coincide with a critical period of brain and cognitive development.¹⁴

A consistent finding in the literature is that children with more severe traumatic brain injury have a greater likelihood of neurocognitive deficits than children with mild TBI. Longitudinal data with 10-year post-injury follow-up confirm this.15–18 Children with mild TBI tend not to exhibit long-lasting impairment. However, some children even with relatively mild trauma can have persistent cognitive problems. Babikian and colleagues studied predictors of these persistent problems. They found that pre-injury variables such as parental education, premorbid behavior and/or learning problems, and school achievement predicted cognitive impairments in children with otherwise mild TBI.¹⁹ Given this information, it might be expected that children with prior subacute sleep disturbances are more likely to report sleep problems with mild TBI than children who otherwise slept well pre-injury.

In evaluating a child with sleep disturbances after a traumatic brain injury, the possibility of confounding depression should be considered. Max and colleagues prospectively studied 177 children with TBI and measured emergence of new-onset depression symptoms 6 months after TBI. The population studied was predominately male with a mean age of 10 years. The authors found an incidence of 11% of ‘novel definite/subclinical depressive disorders.’ Among these children, they further identified subsets of children with non-anxious depression and anxious depression. Emergence of depressive disorder was significantly associated with older age at the time of injury, family history of anxiety disorder, left inferior frontal gyrus (IFG) lesions, and right frontal white matter lesions.²⁰

Children with TBI have been described as having symptoms consistent with attention deficit hyperactivity disorder (ADHD).²¹ A prospective study of 82 children with TBI with a mean age of 5 found that, compared to a control group of children with orthopedic injuries, severe TBI was associated with significantly greater anxiety problems. In addition, over time, children who sustained a severe TBI at an earlier age had significantly higher levels of parent-reported symptoms of ADHD and anxiety.²² Unfortunately, sleep disorders were not specifically evaluated in the methods described.

In the hypersomnolent patient, polysomnography and multiple sleep latency testing should be considered in order to determine the nature of the post-traumatic nocturnal sleep disturbances as well as rule out coexisting pathologies such as obstructive sleep apnea syndrome and periodic limb movement disorder. Comprehensive treatment of hypersomnia in this population will require evaluating the underlying cause of hypersomnia. In children with TBI who have lost consciousness or are recovering from coma it may seem obvious that the hypersomnia is due to the brain injury. However, a careful history must always be taken, and the presence or absence of prior sleep disturbances should be determined. Other causes of hypersomnolence should also be considered in the evaluation of the patient with suspected post-traumatic hypersomnia. Hydrocephalus, subdural hematoma, meningitis, encephalitis, and seizure disorders should be considered as contributing to sleep disturbances.²³ Physical examination can reveal the possibility of minor focal neurologic signs, especially those of brainstem origin. Daytime fatigue may be due to insomnia. The possibility of a medication effect should also be considered. When comprehensive nocturnal polysomnography reveals the presence of sleep-disordered breathing after head trauma, the sleep-related breathing disorders must first be managed before determining the extent to which each comorbid condition contributes to the hypersomnolence. The recognition that head trauma can be a precipitating factor to syndromes leading to excessive daytime sleepiness is important, and a comprehensive evaluation of all patients who exhibit excessive sleepiness after head trauma is needed.

Galland and colleagues conducted a systematic literature review on interventions for sleep problems in children with TBI and found very little evidence-based data in this population.²⁴ They did describe a case report of a 6-year-old boy with a traumatic right-sided hemorrhage in the basal ganglia with pathological crying and poor sleep. The crying decreased and the sleep improved with the use of citalopram.²⁵

Given the description of ADHD complaints in children with TBI, it is not surprising that the use of stimulants in children with TBI has been described and reviewed.26–29 No specific trials of stimulants for hypersomnia in children with TBI were located. In adults, modafinil for hypersomnia associated with TBI has been reported with mixed results.²⁹ The use of modafinil in children has been discouraged due to cutaneous adverse reactions.³⁰ Methylphenidate has been studied in children with TBI predominantly to treat cognitive and behavioral difficulties.^{26,27,31–33} A small randomized trial by Williams and colleagues failed to find a significant improvement of cognitive function in children with TBI using methylphenidate. These children only received 4 days of treatment.³² In a treatment trial by Mahalick and colleagues using methylphenidate in children with TBI a significant improvement in attention and concentration on neuropsychological tests was found. In this placebo-controlled trial, methylphenidate was given for 14 days.³³ Clearly, further research is needed before the use of stimulants in this pediatric population can unequivocally be recommended. A behavioral approach to sleep disorders, especially if insomnia is present, may be a better alternative.