Sleep disorders in chronic traumatic brain injury

STUDY OBJECTIVE

To examine the spectrum of sleep disorders in patients with chronic traumatic brain injury (TBI) and determine if the severity of sleep disorder is related to severity of chronic TBI.

METHODS

Patients who underwent evaluation for sleep disorder/s following a TBI were included in this retrospective analysis. Sixty adult patients with TBI (age 20-69 yr; 38 M and 22 F), who presented with sleep-related complaints 3 months to 2 years following TBI, were studied. None had sleep complaints prior to the TBI. Orophrayngeal, chin, and TMJ examinations were considered benign. The severity of injury was assessed by the Global Assessment of Functioning (GAF) scale. Polysomnograms (PSGs) were performed on 54 patients (90%), 28 of whom underwent multiple sleep latency tests (MSLTs) because they scored >11 on the Epworth Sleepiness Scale (ESS). The Beck Depression Inventory (BDI) scale was administered if there was sleep maintenance insomnia, and the Hamilton Anxiety Scale (HAS) was administered if there was sleep onset insomnia.

RESULTS

The TBI severity was mild in 40%, moderate in 20%, and severe in 40%. The Epworth Sleepiness Scale (ESS) score was elevated (>11) in 52%. Hypersomnia was the presenting complaint in 50%, mostly due to sleep apnea, narcolepsy, and periodic limb movement disorder (PLMD). Insomnia was the presenting complaint in 25%, half with sleep maintenance insomnia and high BDI scores, and the remainder with sleep onset insomnia and high HAS scores. Parasomnia was the presenting complaint in 25%; the most frequent parasomnia was REM behavior disorder (RBD). GAF scores were significantly correlated (p < 0.05) with some of the measures of sleep disruption (stage 1, sleep efficiency, and wake during sleep), but not with others (wake before sleep, stage-shifts, PLMI, PLMA and AHI) on the PSG. Fifty-three percent (15/28) had a mean sleep onset latency <5 minutes, and 32% (9/28), also had two or more sleep onset rapid eye movement periods (SOREMPs) on the MSLT.

CONCLUSION

The results of this study demonstrate that a full spectrum of common sleep disorders occurs in patients with chronic TBI. The severity of chronic TBI as measured by GAF scores is correlated with some of the measures of sleep disruption but not others, indicating a complex and multifactorial pathogenesis.

chi sequences switch the RecBCD helicase-nuclease complex from degradative to replicative modes during the completion of DNA replication

Accurately completing DNA replication when two forks converge is essential to genomic stability. The RecBCD helicase-nuclease complex plays a central role in completion by promoting resection and joining of the excess DNA created when replisomes converge. chi sequences alter RecBCD activity and localize with cross-over hotspots during sexual events in bacteria, yet their functional role during chromosome replication remains unknown. Here, we use two-dimensional agarose gel analysis to show that chi induces replication on substrates containing convergent forks. The induced-replication is processive, but uncoupled with respect to leading and lagging strand synthesis, and can be suppressed by ter sites which limit replisome progression. Our observations demonstrate that convergent replisomes create a substrate that is processed by RecBCD, and that chi, when encountered, switches RecBCD from a degradative to replicative function. We propose that chi serves to functionally differentiate DNA ends created during completion, which require degradation, from those created by chromosomal double-strand breaks, which require resynthesis.