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Cited by 49Traumatic Brain Injury and Neurovascular DisturbancesTraumatic Brain Injury ResearchSleep and Wakefulness Research

Damage to Arousal-Promoting Brainstem Neurons with Traumatic Brain Injury

Open access
Valko, Philipp O., Gavrilov, Yuri V., Yamamoto, Mihoko, Noaín, Daniela, Reddy, Hasini, Haybaeck, Johannes, Weis, Serge, Baumann, Christian R. +1 more·2016·Sleep
DOI 10.5665/sleep.5844PMC PMC4863213
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Abstract

Coma and chronic sleepiness are common after traumatic brain injury (TBI). Here, we explored whether injury to arousal-promoting brainstem neurons occurs in patients with fatal TBI. Postmortem examination of 8 TBI patients and 10 controls. Compared to controls, TBI patients had 17% fewer serotonergic neurons in the dorsal raphe nucleus (effect size: 1.25), but the number of serotonergic neurons did not differ in the median raphe nucleus. TBI patients also had 29% fewer noradrenergic neurons in the locus coeruleus (effect size: 0.96). The number of cholinergic neurons in the pedunculopontine and laterodorsal tegmental nuclei (PPT/LDT) was similar in TBI patients and controls. TBI injures arousal-promoting neurons of the mesopontine tegmentum, but this injury is less severe than previously observed in hypothalamic arousal-promoting neurons. Most likely, posttraumatic arousal disturbances are not primarily caused by damage to these brainstem neurons, but arise from an aggregate of injuries, including damage to hypothalamic arousal nuclei and disruption of other arousal-related circuitries. Direct damage to arousal-promoting neurons is one of several potential causes of chronic sleep-wake disturbances after traumatic brain injury (TBI). We measured the degree of cell loss in arousal structures of the brainstem and hypothalamus in subjects with severe TBI. We found mild neuronal loss in the dorsal raphe nucleus and locus coeruleus, and overall, the monoaminergic and cholinergic arousal nuclei in the rostral brainstem appeared less injured than the arousal structures in the dorsal hypothalamus. The location of these nuclei and local tissue characteristics may better protect these neurons from contusions, shearing, and other trauma-induced forces than those in the hypothalamus.

AI snapshot

Written from the paper’s full text.

TL;DR

Postmortem examination of 8 fatal TBI patients and 10 controls found mild loss of arousal-promoting serotonergic dorsal raphe and noradrenergic locus coeruleus neurons, but not median raphe or cholinergic PPT/LDT neurons. Brainstem arousal nuclei were less injured than hypothalamic arousal nuclei, suggesting posttraumatic arousal disturbances arise from aggregate multi-level injury rather than primarily from brainstem damage.

Key findings

  • TBI patients had 17% fewer serotonergic dorsal raphe nucleus (DRN) neurons than controls (87,733 ± 19,428 vs. 105,584 ± 14,272; P = 0.04; effect size d = 1.25), but similar median raphe nucleus (MRN) neuron numbers (55,375 ± 9,216 vs. 53,706 ± 16,225; P = 0.80).
  • TBI patients had 29% fewer noradrenergic locus coeruleus (LC) neurons than controls (33,259 ± 15,865 vs. 46,928 ± 14,276; P = 0.07; effect size d = 0.96).
  • Cholinergic neuron numbers did not differ in the laterodorsal tegmental nucleus (LDT; 36,027 ± 13,103 vs. 36,825 ± 7,265; P = 0.87) or pedunculopontine tegmental nucleus (PPT; 65,024 ± 11,108 vs. 68,048 ± 13,825; P = 0.61).
  • Hypothalamic neuron loss was more severe (−25.9 ± 14.5%, averaged across HDC, MCH, OxA) than brainstem neuron loss (−9.0 ± 24.4%, averaged across LC, DRN, MRN, PPT, LDT; P = 0.001), with no correlation between hypothalamic and brainstem cell numbers.

Methods

  • Postmortem study of 8 patients with fatal TBI who remained in coma after head injury and died after 20 ± 10 days (range 11–36 days), plus 10 age- and sex-matched controls.
  • Immunohistochemistry for tyrosine hydroxylase, tryptophan hydroxylase, and choline acetyltransferase, with blinded stereological cell counts; H&E-stained sections were also reviewed by a neuropathologist.
  • Group comparisons used Student’s t test, with Cohen’s d for effect size; brainstem findings were compared with previously reported hypothalamic cell counts from the same patients and controls.

Limitations

  • Stated: all patients had severe TBI and died within one month, creating possible inclusion bias and limiting representativeness for all TBI patients; the study focused on neuronal loss rather than axonal injury; no subject survived more than one month, so neuropathology could not be correlated with subjective complaints or sleep physiology, and secondary circuit-level degeneration may not yet be apparent.
  • Evident: the sample was small (8 TBI patients and 10 controls), and the LC finding was borderline by conventional significance (P = 0.07) despite a 29% group difference.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.5665/sleep.5844

Cites

19 of 19 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

7 of 18 cited sources checked · 1 supported · 1 flagged · accuracy not yet measured

  • Premisecitation

    Up to 60% of TBI patients with otherwise excellent neurological recovery report chronic daytime sleepiness or hypersomnia.

    “Even among TBI patients with otherwise excellent neurological recovery, up to 60% report chronic daytime sleepiness or hypersomnia (i.e., increased sleep need per 24 hours). 1”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [1] Imbach, 2015, Increased sleep need and daytime sleepiness 6 months after traumatic brain injury: a prospective controlled clinical trial, Brain source

      The ‘Sleep state misperception after traumatic brain injury’ section reports that 57% of patients had objectively detected daytime sleepiness at six months, but only 19% reported it. The paper therefore makes the contrary point about patient reports; the cited passages also do not establish that these patients had otherwise excellent neurological recovery. (LLM, conf=0.87)

      Checked by a reasoning model — may be wrong.

      Experimental — accuracy not yet measured
  • Premisecitation

    The hypothalamus contains key arousal-promoting neurons, including orexin (hypocretin) neurons in the laterodorsal hypothalamus and histamine neurons in the tuberomammillary nucleus (TMN).

    “The hypothalamus contains key arousal-promoting neurons, including those that make orexin (hypocretin) in the laterodorsal hypothalamus and those that make histamine in the tuberomammillary nucleus (TMN).4”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [4] Saper, 2010, Sleep state switching, Neuron source

      The Wake-promoting networks section identifies orexin (hypocretin) neurons and histaminergic neurons in the TMN as arousal-related populations. It places the orexin neurons in the posterior half of the lateral hypothalamus, not the laterodorsal hypothalamus as the citing sentence states. (LLM, conf=0.89)

      Experimental — accuracy not yet measured
  • Findingown data

    These 2 TBI patients had fewer noradrenergic LC and serotonergic DRN neurons than the other 6 TBI patients.

    “These 2 TBI patients had fewer noradrenergic LC and serotonergic DRN neurons than the other 6 TBI patients.”
    Quote in the paperSubstantial claim
  • Findingown data

    TBI patients had 17% fewer DRN neurons than controls (87,733 ± 19,428 vs. 105,584 ± 14,272, P = 0.04; effect size: d = 1.25).

    “TBI patients had 17% fewer DRN neurons than controls (87,733 ± 19,428 vs. 105,584 ± 14,272, P = 0.04; effect size: d = 1.25)”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The control subjects had no condition affecting arousal-promoting brainstem neurons.
    • Rests on an assumption: Postmortem interval and tissue preservation did not differentially affect neuron counts between TBI and control groups.
  • Findingown data

    Neuron loss was more severe in the hypothalamus (-25.9 ± 14.5%, averaged across HDC, MCH, OxA) than in the brainstem (-9.0 ± 24.4%, averaged across LC, DRN, MRN, PPT, LDT) (P = 0.001).

    “Neuron loss was more severe in the hypothalamus (-25.9 ± 14.5%, as averaged across HDC, MCH, OxA) than in the brainstem (-9.0 ± 24.4%, as averaged across LC, DRN, MRN, PPT, LDT) (P = 0.001)”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The control subjects had no condition affecting arousal-promoting brainstem neurons.
    • Rests on an assumption: Postmortem interval and tissue preservation did not differentially affect neuron counts between TBI and control groups.
  • Classified as probably not a substantial claim. 8
  • May combine two claims. 13

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    In patients with brainstem stroke, acute coma was associated with MRI lesions in the pontine tegmentum extending from the upper pons into the midbrain.

    “Similarly, in patients with brainstem stroke, Parvizi and Damasio found that acute coma was associated with magnetic resonance imaging (MRI) lesions in the pontine tegmentum extending from the upper pons into the midbrain.7”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [7] Parvizi, 2003, Neuroanatomical correlates of brainstem coma, Brain source

      The Results report that coma in patients with brainstem stroke was associated with lesions of the upper pontine tegmentum. But only five of nine coma cases also had midbrain involvement; four had lesions confined to the upper pons. Describing the lesions as extending into the midbrain omits that distinction. (LLM, conf=0.88)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    The underlying neuropathology of posttraumatic sleep-wake disturbances remains little understood, and treatment options are limited.

    “Over the last decade, researchers have developed a better clinical understanding of posttraumatic sleep-wake disturbances, but the underlying neuropathology remains little understood, and treatment options are limited.2,3”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [2] Ouellet, 2015, Sleep-wake disturbances after traumatic brain injury, Lancet Neurol source
    • cites [3] Kaiser, 2010, Modafinil ameliorates excessive daytime sleepiness after traumatic brain injury, Neurology source

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Brainstem neurons were counted in a blinded manner using stereological procedures.

    “We counted brainstem neurons in a blinded manner using the same stereological procedures as previously described.9”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [9] Prins, 2013, The pathophysiology of traumatic brain injury at a glance, Dis Model Mech source

      The cited paper’s section on cerebral glucose metabolism discusses measurements in the brain stem, but not counts of brainstem neurons. Searches for blinded stereological procedures and neuronal counts found no passage describing the method attributed to this source. (LLM, conf=0.76)

      Experimental — accuracy not yet measured

  • Classified as probably not a substantial claim.

    Premisecitation

    It remains unknown whether TBI injures these specific arousal-promoting neurons.

    “Still, it remains unknown whether TBI injures these specific arousalpromoting neurons.”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [6] Crompton, 1971, Brainstem lesions due to closed head injury, Lancet source
    • cites [7] Parvizi, 2003, Neuroanatomical correlates of brainstem coma, Brain source

      The Abstract and Results examine brainstem lesions in patients with stroke, and the Introduction says it was unclear which brainstem nuclei maintain consciousness in humans. Neither addresses whether traumatic brain injury (TBI) injures those neurons. Searches for TBI, traumatic injury, and trauma did not find a passage that settles the claim. (LLM, conf=0.73)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Interpretationcitation

    Additional factors that may protect the brainstem include lower metabolic requirements and a blood supply less likely to be damaged by direct traumatic forces.

    “Additional factors that may protect the brainstem include lower metabolic requirements and a blood supply less likely to be damaged by direct traumatic forces.9”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [9] Prins, 2013, The pathophysiology of traumatic brain injury at a glance, Dis Model Mech source

      The ‘Changes in cerebral glucose metabolism in TBI’ section mentions brain-stem glucose metabolism only in relation to levels of consciousness. The ‘Post-TBI energy crisis’ section discusses cerebral blood flow and metabolic demand generally, but does not say the brainstem has lower metabolic requirements or a blood supply less vulnerable to direct traumatic forces. Searched for brainstem, brain stem, and vascular protection from traumatic forces; our copy does not address the proposed protective factors. (LLM, conf=0.74)

      Experimental — accuracy not yet measured

  • May combine two claims.

    Findingown data

    Only 2 of the 8 TBI patients (25%) showed pathological findings in the brainstem, including acute perivascular 'agonal-type' hemorrhages and microglial nodules in the pons, around the 4th ventricle and in the solitary tract.

    “With H&E staining, only 2 of the 8 TBI patients (25%) showed pathological findings in the brainstem, including acute perivascular”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In 1971, Crompton reported that brainstem lesions occurred in a significant proportion of patients with fatal TBI, most often affecting the tegmental area of the midbrain.

    “In 1971, Crompton reported that brainstem lesions occurred in a significant proportion of patients with fatal TBI, and affected most often the tegmental area of the midbrain.6”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [6] Crompton, 1971, Brainstem lesions due to closed head injury, Lancet source

  • May combine two claims.

    Study design and conductown data

    The Gundersen coefficients of error were <8% for all cell types, indicating good accuracy of the cell counts.

    “The Gundersen coefficients of error were < 8% for all cell types, indicating good accuracy of our cell counts.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    In a comprehensive neuropathology study of 35 TBI patients with vegetative state, brainstem damage was found in only 14% of patients, suggesting that brainstem damage may be less common in TBI than previously thought.

    “Moreover, in a comprehensive neuropathology study of 35 TBI patients with vegetative state who survived for 5 weeks to more than 8 years (24 patients survived at least 3 months), brainstem damage was found in only 14% of patients, suggesting that brainstem damage may be less common in TBI than previously thought.11”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [11] Adams, 2000, The neuropathology of the vegetative state after an acute brain insult, Brain source

  • May combine two claims.

    Interpretationreasoning

    The brainstem may be less vulnerable to contusions, shearing, and other trauma-induced forces than the hypothalamus, possibly due to its location and tissue properties.

    “Possibly, due to its location and tissue properties, the brainstem may be less vulnerable to contusions, shearing, and other trauma-induced forces than the hypothalamus.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The control subjects had no condition affecting arousal-promoting brainstem neurons.
    • Rests on an assumption: Postmortem interval and tissue preservation did not differentially affect neuron counts between TBI and control groups.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Cognitive slowing, impaired attention, and reduced working memory are common after TBI.

    “Cognitive slowing, impaired attention, and reduced working memory are common after TBI, 16”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [16] Murdoch, 1998, Cortical cholinergic dysfunction after human head injury, J Neurotrauma source

  • May combine two claims.

    Study design and conductown data

    None of our TBI subjects survived more than 1 month, so we cannot correlate their neuropathological findings with subjective complaints or sleep physiology.

    “Finally, none of our TBI subjects survived more than 1 month, so we cannot correlate their neuropathological findings with subjective complaints or sleep physiology.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Severe TBI mildly damages neurons of the dorsal raphe nucleus and the locus coeruleus, whereas the MRN, LDT, and PPT are more protected.

    “In conclusion, severe TBI mildly damages neurons of the dorsal raphe nucleus and the locus coeruleus, whereas the MRN, LDT, and PPT are more protected.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The control subjects had no condition affecting arousal-promoting brainstem neurons.
    • Rests on an assumption: Postmortem interval and tissue preservation did not differentially affect neuron counts between TBI and control groups.

  • May combine two claims.

    Interpretationreasoning

    All patients suffered from severe TBI, with death occurring within one month after TBI; this could produce some inclusion bias, and the findings should therefore not be regarded as representative for all TBI patients.

    “All patients suffered from severe TBI, with death occurring within one month after TBI.This could produce some inclusion bias, and our findings should therefore not be regarded as representative for all TBI patients.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    TBI injures arousal-promoting neurons of the mesopontine tegmentum, but this injury is less severe than previously observed in hypothalamic arousal-promoting neurons.

    “TBI injures arousal-promoting neurons of the mesopontine tegmentum, but this injury is less severe than previously observed in hypothalamic arousal-promoting neurons.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The control subjects had no condition affecting arousal-promoting brainstem neurons.
    • Rests on an assumption: Postmortem interval and tissue preservation did not differentially affect neuron counts between TBI and control groups.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    The region near the dorsolateral surface of the mesopontine junction may be vulnerable to direct impact from the tentorium cerebelli.

    “perhaps because this region is vulnerable to direct impact from the tentorium cerebelli.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Most likely, the brainstem is relatively protected from TBI as it may flex less during TBI and is sturdier due to its abundant white matter.

    “Most likely, the brainstem is relatively protected from TBI as it may flex less during TBI and is sturdier due to its abundant white matter.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The control subjects had no condition affecting arousal-promoting brainstem neurons.
    • Rests on an assumption: Postmortem interval and tissue preservation did not differentially affect neuron counts between TBI and control groups.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    We may have overlooked some brainstem damage by focusing on neuronal loss instead of axonal injury.

    “In addition, we may have overlooked some brainstem damage by focusing on neuronal loss instead of axonal injury.”
    Quote in the paperNot a substantial claim
18 of 18

  • The paper relies on this without support.

    The control subjects had no condition affecting arousal-promoting brainstem neurons.

    “We also examined the brainstems of 10 age-and sex-matched controls.”

  • The paper relies on this without support.

    Postmortem interval and tissue preservation did not differentially affect neuron counts between TBI and control groups.

    “We examined 8 patients with fatal TBI and adequately preserved brainstems throughout the entire midbrain and pons.”
2 of 2

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • A reported survival time exceeds one month

    Minor

    The reported range includes a patient who died 36 days after injury, contradicting the statement that all patients died within one month.

1 of 1

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Authors
Valko, P. O., Gavrilov, Y. V., Yamamoto, M., Noaín, D., Reddy, H., Haybaeck, J., Weis, S., Baumann, C. R., & Scammell, T. E.
Affiliations
  • Beth Israel Deaconess Medical Center (US)
  • Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA
  • University of Zurich (CH)
  • Medical University of Graz (AT)
  • Johannes Kepler University of Linz (AT)
Corresponding author
Valko, Philipp O.
ORCID
Venue
Sleep
Publisher
Oxford University Press (OUP)
Published
2016-06-01
Volume
39
Issue
6
Pages
1249-1252
ISSN
  • 0161-8105 (ISSN-L)
  • 1550-9109
DOI
10.5665/sleep.5844
PMC
PMC4863213
OpenAlex
W2471525840
Semantic Scholar
08a7a22fb5d60f27f75fa1135bd2cae1a7c7abc8
Cited by
49
References
18
Citations by year
2026: 4 · 2025: 6 · 2024: 5 · 2023: 4 · 2022: 5 · 2021: 8 · 2020: 1 · 2019: 3 · 2018: 8 · 2017: 4 · 2016: 1
FWCI
3.44
Type
journal article
Language
en
Open access
Locations
  • SLEEP (publishedVersion)
  • PubMed (publishedVersion)
  • reroDoc Digital Library (submittedVersion)
  • Zurich Open Repository and Archive (University of Zurich) (submittedVersion, other-oa)
  • Europe PMC (PubMed Central) (submittedVersion)
  • PubMed Central (submittedVersion)
  • Zurich Open Repository and Archive (University of Zurich)
Funders
  • National Science Foundation
  • Purdue University
  • Purdue Pharma
  • Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung (32003B, 125504)
  • Eisai
  • Universität Zürich
Topics
  • Health Sciences › Medicine › Neurology › Traumatic Brain Injury and Neurovascular Disturbances
  • Health Sciences › Medicine › Epidemiology › Traumatic Brain Injury Research
  • Life Sciences › Neuroscience › Cognitive Neuroscience › Sleep and Wakefulness Research
Keywords
traumatic brain injury, brainstem, dorsal raphe nucleus, locus coeruleus, pedunculopontine nucleus, laterodorsal tegmental nucleus, serotonergic neurons, noradrenergic neurons, cholinergic neurons, neuronal loss, coma, sleep-wake disturbances, hypothalamus
MeSH terms
Brain Injuries, Traumatic, Arousal, Autopsy, Brain Stem, Humans, Hypothalamus, Locus Coeruleus, Neural Pathways, Neurons, Pons, Case-Control Studies, Serotonergic Neurons, Cholinergic Neurons, Adrenergic Neurons, Dorsal Raphe Nucleus

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