Disembodied Mind: Cortical Changes Following Brainstem Injury in Patients with Locked-in Syndrome

Locked-in syndrome: A qualitative study of a life story

INTRODUCTION

Locked-in syndrome (LIS) is characterized by tetraplegia, anarthria, paralysis of cranial nerves, and facial musculature, with the preservation of consciousness and cognitive abilities, as well as vertical eye movements and eyelid movements, hearing, and breathing. Three types of LIS are distinguished: classic, incomplete, and total. The aim of the present study was to describe the life history of a person with LIS, as well as the wife's experience and perspective of this life history.

METHODS

A qualitative life history study was conducted with two participants: a 54-year-old man diagnosed with LIS and his 50-year-old wife. Data were collected through interviews and autobiographical documents submitted by the participants and analyzed following Braun and Clarke's method of inductive thematic analysis.

RESULTS

Five main themes were identified: (1) how to understand and overcome the new situation; (2) the process of care and rehabilitation; (3) communication; (4) writing as a way of helping oneself and others; and (5) personal autonomy and social participation.

CONCLUSION

The participants valued the support of their friends and family in the acceptance stage of the new situation, giving special importance to the communication skills and medical attention received after diagnosis.

Diffusion tensor imaging reveals diffuse white matter injuries in locked-in syndrome patients

Locked-in syndrome (LIS) is a state of quadriplegia and anarthria with preserved consciousness, which is generally triggered by a disruption of specific white matter fiber tracts, following a lesion in the ventral part of the pons. However, the impact of focal lesions on the whole brain white matter microstructure and structural connectivity pathways remains unknown. We used diffusion tensor magnetic resonance imaging (DT-MRI) and tract-based statistics to characterise the whole white matter tracts in seven consecutive LIS patients, with ventral pontine injuries but no significant supratentorial lesions detected with morphological MRI. The imaging was performed in the acute phase of the disease (26 ± 13 days after the accident). DT-MRI-derived metrics were used to quantitatively assess global white matter alterations. All diffusion coefficient Z-scores were decreased for almost all fiber tracts in all LIS patients, with diffuse white matter alterations in both infratentorial and supratentorial areas. A mixture model of two multidimensional Gaussian distributions was fitted to cluster the white matter fiber tracts studied in two groups: the least (group 1) and most injured white matter fiber tracts (group 2). The greatest injuries were revealed along pathways crossing the lesion responsible for the LIS: left and right medial lemniscus (98.4% and 97.9% probability of belonging to group 2, respectively), left and right superior cerebellar peduncles (69.3% and 45.7% probability) and left and right corticospinal tract (20.6% and 46.5% probability). This approach demonstrated globally compromised white matter tracts in the acute phase of LIS, potentially underlying cognitive deficits.

Cortical Brain Changes in Patients With Locked-In Syndrome Experiencing Hallucinations and Delusions

Previous evidence suggests that hallucinations and delusions may be detected in patients with the most severe forms of motor disability including locked-in syndrome (LIS). However, such phenomena are rarely described in LIS and their presence may be underestimated as a result of the severe communication impairment experienced by the patients. In this study, we retrospectively reviewed the clinical history and the neuroimaging data of a cohort of patients with LIS in order to recognize the presence of hallucinations and delusions and to correlate it with the pontine damage and the presence of any cortical volumetric changes. Ten patients with LIS were included (5 men and 5 women, mean age 50.1 ± 14.6). According to the presence of indicators of symptoms, these patients were categorized as hallucinators (n = 5) or non-hallucinators (n = 5). MRI images of patients were analyzed using Freesurfer 6.0 software to evaluate volume differences between the two groups. Hallucinators showed a selective cortical volume loss involving the fusiform (p = 0.001) and the parahippocampal (p = 0.0008) gyrus and the orbital part of the inferior frontal gyrus (p = 0.001) in the right hemisphere together with the lingual (p = 0.01) and the fusiform gyrus (p = 0.01) in the left hemisphere. Moreover, a volumetric decrease of bilateral anterior portions of the precuneus was recognized in the hallucinators (right p = 0.01; left p = 0.001) as compared to non-hallucinators. We suggested that the presence of hallucinations and delusions in some LIS patients could be accounted for by the combination of a damage of the corticopontocerebellar pathways with cortical changes following the primary brainstem injury. The above areas are embedded within cortico-cortical and cortico-subcortical loops involved in self-monitoring and have been related to the presence of hallucinations in other diseases. The two main limitations of our study are the small sample of included patients and the lack of a control group of healthy individuals. Further studies would be of help to expand this field of research in order to integrate existing theories about the mechanisms underlying the generation of hallucinations and delusions in neurological patients.

Disorders of Consciousness: Painless or Painful Conditions?-Evidence from Neuroimaging Studies

The experience of pain in disorders of consciousness is still debated. Neuroimaging studies, using functional Magnetic Resonance Imaging (fMRI), Positron Emission Tomography (PET), multichannel electroencephalography (EEG) and laser-evoked potentials, suggest that the perception of pain increases with the level of consciousness. Brain activation in response to noxious stimuli has been observed in patients with unresponsive wakefulness syndrome (UWS), which is also referred to as a vegetative state (VS), as well as those in a minimally conscious state (MCS). However, all of these techniques suggest that pain-related brain activation patterns of patients in MCS more closely resemble those of healthy subjects. This is further supported by fMRI findings showing a much greater functional connectivity within the structures of the so-called pain matrix in MCS as compared to UWS/VS patients. Nonetheless, when interpreting the results, a distinction is necessary between autonomic responses to potentially harmful stimuli and conscious experience of the unpleasantness of pain. Even more so if we consider that the degree of residual functioning and cortical connectivity necessary for the somatosensory, affective and cognitive-evaluative components of pain processing are not yet clear. Although procedurally challenging, the particular value of the aforementioned techniques in the assessment of pain in disorders of consciousness has been clearly demonstrated. The study of pain-related brain activation and functioning can contribute to a better understanding of the networks underlying pain perception while addressing clinical and ethical questions concerning patient care. Further development of technology and methods should aim to increase the availability of neuroimaging, objective assessment of functional connectivity and analysis at the level of individual cases as well as group comparisons. This will enable neuroimaging to truly become a clinical tool to reliably investigate pain in severely brain-injured patients as well as an asset for research.