Locked-In Syndrome

Locked-in syndrome (LIS) is a diagnosis which encapsulates patients who are alert, cognitively conscious and capable of communication but are unable to move or speak (American Congress of Rehabilitation Medicine, 1995). LIS is most often the result of a ventral pons lesion characterized by motor de-efferentation producing paralysis of all four limbs (American Congress of Rehabilitation Medicine, 1995; Smith and Delargy, 2005). There are difference subcategories, described below, that breakdown the extent of motor and verbal impairment, which can be complete or partial (American Congress of Rehabilitation Medicine, 1995).

The three categories of LIS:

1. Classic—Quadriplegia and anarthria with preserved consciousness and vertical eye movement
2. Incomplete—The same as classic but with remnants of voluntary movement other than vertical eye movement
3. Total—Total immobility and inability to communicate, with full consciousness (Smith and Delargy, 2005).

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Clinically Relevant Anatomy

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Epidemiology

The precise prevalence rate of LIS is not specifically documented in the literature and the incidence rate is thought to be underestimated. However, the population of patients with LIS as discussed in the literature is found to have relatively equal frequency amongst men and women and occurs most frequently between the ages of 41-52 years (Leon-Carrion et al, 2002). Furthermore, 60% of cases LIS is caused by a basilar artery occlusion or pontine hemorrhage, but it can also be caused by traumatic brain injury (TBI) (Schnakers et al., 2008; casanova, 2003).

Mechanism of Injury / Pathological Process

The most common etiology of LIS it due to ventral pontine strokes, although more than 20 different mechanisms of LIS have been described (Doble, Haig, Anderson, and Katz, 2003). Most commonly ventral pontine infarction is the result of basilar artery occlusion. (Casanova et al., 2003). Less frequent causes of LIS include tumours, infection, trauma, lesions, and hypotensive events in other areas of the brainstem (Doble, Haig, Anderson, and Katz, 2003).

Clinical Presentation

Early literature estimated that LIS had a mortality rate of ~60%, with mortality highest in the first six months (Doble, Haig, Anderson, & Katz, 2003). However, more recent studies indicate the 5-year survival rate to be greater than 80% (Doble et al., 2003). It has been demonstrated that patients have greater rates of survival if they are younger at the time of insult and if they received rehabilitation and nursing care early after their diagnosis (Smith & Delargy, 2005). Mortality rates have been found to decrease to 14% in those patients who were able to begin their rehabilitation in the acute stage of the syndrome (Smith & Delargy , 2005). Although, the majority of people with LIS remain in the locked-in stage or have serious impairments (Smith & Delargy, 2005).

A retrospective study focused on the impairments present in those with locked-in syndrome and found that neurological impairments remained in all subjects and that the majority of patients had poor object manipulation and oral communication (Doble et al., 2003). However, functional gains were evident because many individuals were able to the decrease their use of medical devices such as feeding tubes and urinary catheters (Doble et al., 2003). Moreover, communication was maintained in patients through eye or facial movements, computer technology, or letter boards, where they were able to use their upper limbs to point to a respective letter (Doble et al., 2003). It is important to note that those with LIS will have a high burden of care and will require the support of extended care facilities or family members (Doble et al., 2003). Finally, those who did pass away had various complications including heart disease, multisystem failure, pneumonia, respiratory failure, internal bleeding and aspiration (Doble et al., 2003).

Diagnostic Procedures

The neurobehavioral criteria for diagnosing LIS consist of:

1. Maintained eye opening
2. Basic cognitive abilities are preserved
3. Severe hyophonia or aphonia
4. Quadriparesis or quadriplegia
5. Communication through vertical or lateral eye-movement or blinking (American Congress of Rehabilitation Medicine, 1995).
   
   

Diagnosis for LIS is a long process and is often initiated when a family member or care staff report they have noticed a sign from the patient that the individual is aware (Smith & Delargy, 2005). With the knowledge that LIS affects the brainstem, physicians must do neurological testing and should focus on the patient’s eye movements (Barbic et al., 2012). A brainstem lesion is determined if the horizontal eye movement is abnormal with unilateral or bilateral conjugate gaze or with the absence of abduction of either eye (Barbic et al., 2012).

Diagnosis of LIS is often overseen if vertical voluntary eye movement is not assessed in the unresponsive patient (Smith & Delargy, 2005). Testing vertical voluntary eye movement can be achieved through having the patient voluntarily track your finger movement (Barbic et al., 2012). If it is suspected that a patient has LIS, they must be immediately referred for neurologic and neuroradiologic consultation (Barbic et al., 2012). A MRI must also be done to confirm a lesion in the ventral pons and at that point if not already completed, vertical eye movement should be assessed to determine if this voluntary movement is retained (Smith & Delargy, 2005).

Outcome Measures

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Management / Interventions

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Differential Diagnosis

LIS can present in a similar clinical manner to various other conditions and therefore should be thought of while assessing a patient, in order to provide a correct diagnosis (Laureys, 2010). Potential alternate disorders or conditions that present in a similar clinical manner to LIS include Guillain-Barre syndrome, myasthenia gravis, poliomyelitis, polyneuritis, or bilateral brainstem tumours (Laureys, 2010).Furthermore, LIS could be mistaken as Akinetic mutism, which is a rare neurological condition where the individual will not move (akinetic) or talk (mute) despite being awake (Laureys, 2010).

Finally, LIS diagnosis can be missed and mistaken as being in a vegetative state (Laureys, 2010). This is even more common in those with vision or hearing problems, which makes the LIS diagnosis even more difficult (Laureys, 2010).

Key Evidence

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Case Studies

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