The Relation Between Loss of Consciousness, Severity of Traumatic Brain Injury, and Injury of Ascending Reticular Activating System in Patients With Traumatic Brain Injury.

OBJECTIVE: Loss of consciousness is an indicator of the severity of traumatic brain injury and the ascending reticular activating system has been considered as a main structure for consciousness. However, no study on the relation between loss of consciousness and ascending reticular activating system injury in traumatic brain injury has been reported. We investigated the relation between loss of consciousness, severity of traumatic brain injury, and ascending reticular activating system injury using diffusion tensor tractography. DESIGN: One hundred twenty patients were recruited. Three components of ascending reticular activating system, fractional anisotropy, and tract volume were measured. RESULTS: In lower dorsal and ventral ascending reticular activating system, fractional anisotropy and tract volume value in mild group were higher than those of moderate and severe groups, and there was no difference between moderate and severe groups. In upper ascending reticular activating system, fractional anisotropy value in mild group was higher than in moderate group, and it was higher than in moderate group than in severe group. Tract volume value in mild group was higher than in severe group. Loss of consciousness showed moderate negative correlations with tract volume value of lower dorsal ascending reticular activating system (r = -0.348), fractional anisotropy value of lower ventral ascending reticular activating system (r = -0.343), and fractional anisotropy value of upper ascending reticular activating system (r = -0.416). CONCLUSIONS: Injury severity was different among the three traumatic brain injury groups in upper ascending reticular activating system but did not differ between moderate and severe groups in lower dorsal and ventral ascending reticular activating system.

Bilateral surgical damage of the central tegmental tract resulting in bilateral hypertrophic olivary degeneration: An MRI case report.

Hypertrophic olivary degeneration (HOD) is a rare trans-synaptic neuronal degeneration of the inferior olivary nucleus caused by an injury to the dentato-rubro-olivary connection, also known as Guillain-Mollaret triangle. It leads to hypertrophy of the affected nucleus rather than atrophy and is characterized by hyperintensity on T2-weighted images. Unilateral and bilateral cases are described. We present a case of a 70-year-old patient affected by a tumor inside the fourth ventricle who suffered from diplopia and right seventh cranial nerve palsy. He underwent surgery and developed left seventh cranial nerve palsy. Three months after resection, magnetic resonance imaging revealed the appearance of bilateral HOD. This is the first report of bilateral HOD occurrence after surgical bilateral damage of the rubro-olivary fibers running in central tegmental tracts.

Injury of the lower ascending reticular activating system in patients with pontine hemorrhage: Diffusion tensor imaging study.

Many studies have reported about injury of the ascending reticular activating system (ARAS) in patients with various brain pathologies, using diffusion tensor tractography (DTT); however, little is known about injury of the ARAS in patients with pontine hemorrhage. In this study, using DTT, we attempted to investigate injury of the lower ventral and dorsal ARAS in patients with pontine hemorrhage. Twenty-three consecutive patients with pontine hemorrhage and 14 control subjects were recruited into this study. The patients were classified into 2 subgroups on the basis of the preservation of arousal: subgroup A (14 patients)-intact arousal, subgroup B (9 patients)-impaired arousal. The lower ventral and dorsal ARAS between the pontine reticular formation with hypothalamus and thalamic intralaminar nucleus were reconstructed. Fractional anisotropy (FA), mean diffusivity (MD), and tract volume (TV) values were measured. The TVs of the lower ventral and dorsal ARAS were significantly lower in subgroup B than in the subgroup A and control group (P < 0.05). In terms of FA value, the lower dorsal ARAS were significantly lower in subgroup A and subgroup B than in the control group (P < 0.05). In conclusion, injury of the lower ventral and dorsal ARAS was demonstrated in patients with impaired arousal following pontine hemorrhage. We believe that analysis of the ARAS using DTT would be helpful in evaluation of patients with impaired consciousness after pontine hemorrhage.

Recovery of Hypersomnia Concurrent With Recovery of an Injured Ascending Reticular Activating System in a Stroke Patient: A Case Report.

We report on a stroke patient who showed recovery of hypersomnia concurrent with the recovery of an injured ascending reticular activating system (ARAS), which was demonstrated by diffusion tensor tractography (DTT).A 70-year-old female patient underwent coiling of the left ruptured posterior communicating artery after subarachnoid hemorrhage and both extraventricular drainage for management of an intraventricular hemorrhage. At 2 months after onset, when she started rehabilitation, she exhibited intact consciousness, with the full score on the Glasgow Coma Scale: 15. However, she showed severe hypersomnia: she always fell asleep without external stimulation and the Epworth Sleepiness Scale (EPS) score was 24 (full score: 24, cut off for hypersomnia: 10). She underwent comprehensive rehabilitative therapy, including neurotropic drugs, physical therapy, and occupational therapy. Her hypersomnia has shown improvement as 14 (3 months after onset), 11 (4 months after onset), 7 (12 months after onset), and 6 (24 months after onset), respectively.On 2-month DTT, narrowing of both lower dorsal and ventral ARASs was observed on both sides: in particular, among 4 neural tracts of the lower ARAS, the right lower ventral ARAS was the narrowest. By contrast, on 24-month DTT, the 4 narrowed neural tracts of both lower dorsal and ventral ARASs were thickened compared with those of 2-month DTT.Recovery of hypersomnia with recovery of an injured lower ARAS on DTT was observed in a stroke patient. Our results suggest that evaluation of the lower ARAS using DTT might be useful for stroke patients with hypersomnia.

Recovery of injured lower portion of the ascending reticular activating system in a patient with traumatic brain injury.

The authors report on a patient with traumatic brain injury who showed recovery of an injured lower portion of the ascending reticular activating system (ARAS) between the pontine reticular formation and the thalamus. A 57-yr-old male patient experienced head trauma. After 4 mos from onset, he exhibited impaired alertness, with a score of 7 on the Glasgow Coma Scale. At 40 mos after onset, the patient had a full Glasgow Coma Scale score of 15. The lower portion of the ARAS was reconstructed using the probabilistic tractography method. On 4-mo diffusion tensor tractography, the fractional anisotropy and the tract volume of the lower portion of the right ARAS were lower by more than 2 SDs of those of control subjects. By contrast, on 40-mo diffusion tensor tractography, the fractional anisotropy and the tract volume values of the lower portion of the right ARAS were within 2 SDs of those of the control subjects. The increment fractional anisotropy and the FV value of the lower portion of the right ARAS on 40-mo diffusion tensor tractography indicated recovery of the injured lower ARAS. As a result, recovery of an injured lower portion of the ARAS in a patient with traumatic brain injury was demonstrated.