Locked-in patients are not restricted in their higher neuronal functions when locked into a body that has become incapable of movement. While the former had to face miserable living circumstances and were moved to nursing homes, they can now be re-integrated into life with sophisticated therapies and techniques.
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Locked-in syndrome after basilary artery thrombosis by mucormycosis masquerading as meningoencephalitis in a lymphoma patient: An MRI of the brain, T2 W images, axial (A) and coronal view (B). Clearly visible in the right portion of the pons is a hyperintense area (white arrows), according to pathologic findings (mucormycosis localisation).”
by Guldenmund P, Stender J, Heine L, Laureys S – Crit Care Res Pract (2012). License: CC BY 3.0

Definition of the Locked-in Syndrome

Locked-in syndrome interrupts corticospinal and bulbar tracts in the ventral part of the pons. Spastic tetraplegia, cerebral nerve disruption (loss of pharynx, larynx, chewing and facial musculature) and thus also the inability to speak. Horizontal eye movements are not possible.

On the other hand, consciousness and language comprehension, vertical eye movements and eyelid closure, as well as breathing regulation, are preserved. Sensitivity and algesia (pain perception) are usually normal.

Background of the Locked-in Syndrome

Locked-in syndromes (LISs) are probably as old as humanity itself. Already, Alexandre Dumas mentions this phenomenon in his book “The Count of Monte Christo”; therefore, it was often referred to as Monte-Christo syndrome. Clinically, the syndrome was first described in 1966 by Plum and Posner.

Etiology and pathophysiology of the Locked-in Syndrome 

The misjudged clinical picture is often due to a bilateral lesion of the ventral pons, usually by occlusion of the basilar artery, or by a central pontine myelinolysis. Also, as a result of brain stem bleeding or contusions, tumors or brainstem nephroliths, a locked-in syndrome is possible. In the context of amyotrophic lateral sclerosis (ALS), a state corresponding to the locked-in syndrome can also occur in the terminal stage.

Affected by the lesion are the long tracts (tractus corticospinalis and corticonuclearis), the abducens nucleus and the paramedian pontine formation reticularis (PPRF), while, in the rostral interstitial nucleus of the fasciculus longitudinalis medialis, occurring vertical eye movements are still possible.

Symptoms of the Locked-in Syndrome

How the Locked-in syndrome manifests itself

Initially, the patients are frequently in coma, with the vigilance rapidly improving in the case of ischemia. The awake, receptive and cognitively not impaired patient can see and hear his environment. However, he shows a spastic tetraplegia, is unable to speak, swallow, or show facial expressions. There is a horizontal view paresis on both sides, blinking and corneal reflex is canceled.

On the extremities, there are strecksynergysms, which can be triggered by the frequently obtained sensitivity.

Vertical eye movement and, in part, blinking of the eye are preserved, which can be used for communication.

Recurrent features of locked-In syndromes are:

  • Tetraplegia/tetraparalysis
  • Paralysis of almost all motor cranial nerves
  • Necessity of artificial respiration (acute phase)
  • Alertness of the patient
  • Perception of the environment

In order to clarify the last two points, electrophysiological methods, such as evoked potentials to somatosensible and acoustic stimuli, can help out (SEPs and AEPs).

Image: “Spontaneous brain activity in VS/UWS, MCS, locked-in syndrome, and health, as seen with PET. A triangle is drawn around the precuneus; an area whose spontaneous metabolic intensity is indicative of the level of consciousness.” by Guldenmund P, Stender J, Heine L, Laureys S – Crit Care Res Pract (2012). License: Copyright Policy – open-access

Differential diagnoses of the Locked-in Syndrome 

Similar symptoms to Locked-in Syndrome 

  • Guillain-Barré syndrome: Autoimmune reaction to peripheral nervous tissue; when motor nerve neurons are involved, similar symptoms can occur.
  • Apallic syndrome: (Syn. Coma vigile, persistent vegetative status, so-called “wake coma”). The apallic patient is awake, but does not consciously perceive his environment and himself. The eyes are open, but no visual fixation is possible, no cognition takes place.
  • Akinetic Mutism: There is no motor response to strong pain stimuli; caudal brain stem reflexes are preserved. The horizontal view function is intact.

The distinction is important in order to meet the locked-In patient, who clearly perceives his environment, is able to feel pain, and can be questioned for treatment and therapy.

Therapy of the Locked-in Syndrome

In addition to the causative treatment (e.g. brainstem ischemia), communication aids are used at an early stage (e.g., computer-assisted). In the acute phase of a stroke, most patients are dependent on ventilation. Since the patients cannot swallow, a tracheostomy is necessary to protect against aspiration. If an improvement in the state of health should take place, a weaning of the ventilation can finally take place.

Ways to communicate with locked-in patients

The first step in dealing with a locked-in patient is to find a well-functioning coding in order to communicate. In most cases, an eye movement is used as a code. A movement upwards means YES, down NO.

In the well-known case of “Elle” editor Jean-Dominique Bauby, the lid closure was used as a communication path. Bauby was able to dictate his book “Butterfly and Diver Bell” by means of a series of letters that have been read to him. He winked at the letter he needed. Bauby himself described the opening and closing of the eyelid as a wing flap of a butterfly with which he could recapture the world.

Former creative director Georg Claus also suffered a lock-in syndrome. He managed to move his head easily. He then invented a method by which he used glasses with a built-in laser pointer to point to letter and symbol panels. With this method, he has created his own LIS Help website.

Improving the performance of an EEG-based motor imagery brain computer interface using task evoked changes in pupil diameter: Common Spatial Pattern Maps. The Figure illustrates a set of common spatial patterns (CSPs) filters of a single participant in the study. The CSPs are optimized for the discrimination of left hand motor imagery from a control rest condition.”
by Rozado D, Duenser A, Howell B – PLoS ONE (2015. License: CC BY 4.0

History and forecast

The mortality rate of patients with locked-in syndrome was still over 90% in the 1970s, but has fallen to less than 50% due to advances in intensive care medicine.

Often, the phase of the “Locked-in Syndrome” is a transitory stage (transient locked-in syndrome). Through persistent and intensive rehabilitation measures, good results can be achieved here, and by means of many years of therapy, many affected individuals are again able to live independently.

However, there are also cases of a chronic locked-in syndrome.

An emotional perspective

For a long time, the condition of an LIS was considered to be a severe one. Those who were condemned to passivity could do nothing more than wait and watch what was going on with them. Accordingly, Professor Werner Hacke, Director of the Neurological Clinic Heidelberg, writes: “We, therefore, sedate patients […] always deeply, in order not to let them experience the certainly tormenting inclination in their irreversible paralysis.”

However, researchers at the University of Liège have further investigated the emotional state of patients and have questioned the LIS sufferers themselves. What had previously been speculatively supposed to be “certainly agonizing” has not been confirmed:

Only 28% consider themselves unhappy. On the other hand, 72% of LIS patients considered themselves happy.

Further questions concerned fears, pain and suicidal tendencies.

According to this research group, the satisfaction of the patients depends on the quality of the care; on the other hand, the affected persons need to be familiarized with the new situation. A decision on euthanasia should not be taken too early. Of 59 respondents, only four persons had wanted euthanasia.

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