Locked-in syndrome (LIS) is a rare, devastating neurological condition defined by quadriplegia, anarthria, and lower cranial nerve paralysis with fully preserved consciousness. [1-2] The hallmark is a patient who appears unresponsive but is cognitively intact, communicating only through vertical eye movements and blinking. [3-4] It is most commonly caused by basilar artery occlusion leading to ventral pontine infarction and represents a critical, time-dependent diagnosis in the emergency department. [3][5]
1. History
- Sudden onset of inability to move, speak, or swallow — often preceded by prodromal symptoms of posterior circulation ischemia (dizziness, diplopia, dysarthria, ataxia, perioral paresthesias) [6-7]
- Timing: hyperacute onset suggests embolic occlusion; stuttering/progressive onset suggests in-situ basilar artery thrombosis [8]
- Prior TIAs in the posterior circulation (vertigo, drop attacks, bilateral visual disturbance) [6]
- Mechanism of injury: spontaneous vs. traumatic (TBI accounts for ~14% of cases) [4]
- Assess for preceding headache (vertebral artery dissection), neck manipulation, or recent procedures
- Medication history: anticoagulants, antiplatelets, oral contraceptives
- Last known well time — critical for thrombolytic/endovascular eligibility [5][9]
2. Alarm Features
- Sudden unresponsiveness with preserved eye opening — do NOT assume coma [3][10]
- Acute quadriplegia with anarthria and apparent "coma" — must test vertical eye movements and blinks to command [3]
- Respiratory failure requiring emergent intubation (loss of voluntary respiratory control) [2]
- Rapidly progressive brainstem signs (cranial nerve palsies, bilateral motor deficits)
- Any patient with sudden altered mental status and no clear metabolic cause warrants urgent vascular imaging to exclude basilar artery occlusion [10]
3. Medications
- Acute treatment:
- IV alteplase (tPA) within 4.5 hours of symptom onset — case reports of dramatic improvement in LIS [5]
- Endovascular thrombectomy (EVT) for basilar artery occlusion: associated with improved functional outcomes and decreased mortality (cOR 2.68 for improved mRS) [9][11]
- Antiplatelet therapy (aspirin) and anticoagulation as indicated by stroke etiology [12]
- Supportive/chronic:
- Anxiolytic therapy — patients are fully conscious and terrified; consider benzodiazepines acutely [13]
- DVT prophylaxis (heparin/LMWH)
- Antispasticity agents (baclofen, tizanidine) as needed
- Antidepressants — depression reported in ~12.5% of chronic LIS patients [4]
- Contraindicated/caution: Sedating medications may mask the ability to detect preserved consciousness; avoid unnecessary sedation [14]
4. Diet
- NPO acutely — severe dysphagia and absent gag/swallow reflex [2]
- Early enteral nutrition via nasogastric or PEG tube
- Swallowing evaluation (videofluoroscopy or FEES) before any oral feeding trial — 42% of patients may eventually recover swallow function [15]
- Long-term: aspiration precautions; reinstatement of oral feeding only after formal swallow assessment [2]
- Adequate hydration and nutritional support are critical for rehabilitation outcomes
5. Review of Systems
- Neurologic: Assess for any residual voluntary movement (distal extremities, facial muscles), vertical gaze, blinking to command
- Respiratory: Ventilatory dependence, ability to breathe spontaneously, secretion management
- GI: Bowel function, constipation (neurogenic bowel), aspiration risk
- GU: Urinary retention, neurogenic bladder
- Psych: Depression, anxiety, emotional lability (patients are fully aware) [4][13]
- Ophthalmologic: Horizontal gaze palsy, corneal exposure, dry eyes [2]
- MSK: Contractures, spasticity, orthostatic intolerance [2]
6. Collateral History and Family History
- Collateral from witnesses regarding onset time, preceding symptoms, and last known well time — essential for reperfusion eligibility
- Prior history of stroke, TIA, atrial fibrillation, or vascular disease
- Family history of hypercoagulable states, premature atherosclerosis, connective tissue disorders (vertebral artery dissection risk)
- Social history: smoking, substance use, oral contraceptive use
- Advance directives and goals of care — critical early discussion given severity of condition [16]
7. Risk Factors
- Atherosclerotic disease: Hypertension, diabetes, hyperlipidemia, smoking — most common cause of basilar artery stenosis/thrombosis [7-8]
- Cardioembolism: Atrial fibrillation, valvular disease, patent foramen ovale [7][17]
- Vertebral artery dissection: Younger patients, neck trauma, chiropractic manipulation [8]
- Hypercoagulable states: Antiphospholipid syndrome, malignancy
- Demographics: Median age ~55 years; male predominance (70% in population-based data) [18]
- Intracranial atherosclerosis more common in Black African and East Asian populations [7]
8. Differential Diagnosis
This is the most critical clinical distinction — LIS is frequently misdiagnosed as coma or vegetative state, with a mean diagnostic delay of ~79 days. [4]
- Coma — eyes closed, unarousable; no voluntary eye movements. LIS patients open eyes spontaneously and follow commands with vertical gaze [14]
- Vegetative state (unresponsive wakefulness syndrome) — eyes open with sleep-wake cycles but no purposeful behavior. LIS has intact cognition and purposeful eye movements [14]
- Minimally conscious state — inconsistent but reproducible purposeful behavior. LIS has consistent, reliable responses [19]
- Akinetic mutism — bilateral frontal/cingulate lesions; reduced initiation of movement and speech but some motor capacity preserved; cognitive impairment usually present [14][20]
- Severe Guillain-Barré syndrome — ascending paralysis with areflexia; peripheral nerve findings; CSF albuminocytologic dissociation; may mimic LIS [14]
- Myasthenia gravis crisis — fatigable weakness, ptosis, bulbar symptoms; responds to edrophonium/neostigmine [14]
- End-stage ALS — progressive motor neuron disease leading to total paralysis with preserved cognition [21]
- Central pontine myelinolysis — history of rapid sodium correction; osmotic demyelination on MRI
- Brainstem encephalitis — subacute onset, CSF pleocytosis
9. Past Medical History
- Prior stroke or TIA (especially posterior circulation)
- Atrial fibrillation or other cardiac arrhythmias
- Hypertension, diabetes, hyperlipidemia
- Known vertebrobasilar stenosis or intracranial atherosclerosis
- Connective tissue disorders (Ehlers-Danlos, Marfan — dissection risk)
- Prior neurosurgical or endovascular procedures [8]
- History of coagulopathy or anticoagulant use
10. Physical Exam
- Vital signs: Hypertension (often severe), bradycardia or tachycardia, respiratory failure
- Level of consciousness: Patient appears comatose but eyes are open; must test for voluntary vertical eye movements and blinking to command — this is the key to diagnosis [3][14]
- Cranial nerves:
- Pupils: often pinpoint (pontine lesion) but reactive [14]
- Horizontal gaze: absent (bilateral PPRF/abducens involvement)
- Vertical gaze: preserved (supranuclear pathways rostral to lesion)
- Facial paralysis: bilateral lower motor neuron pattern
- Absent gag, cough, and swallow reflexes
- Motor: Quadriplegia with bilateral extensor plantar responses; no voluntary limb movement (incomplete LIS may have some distal movement) [2]
- Sensory: Intact — patients feel pain and all sensory modalities (nearly 100% report sensitivity to touch) [4]
- Oculomotor exam is the single most important component — failure to perform it is the most common reason for missed diagnosis [3]
11. Lab Studies
- Stat labs: CBC, BMP, coagulation studies (PT/INR, aPTT), glucose — rule out metabolic causes of unresponsiveness [22]
- Troponin (cardiac source of embolism)
- Lipid panel, HbA1c (vascular risk stratification)
- Toxicology screen (rule out toxic coma mimics)
- Blood cultures if infection suspected
- Hypercoagulable workup in younger patients (antiphospholipid antibodies, protein C/S, factor V Leiden)
- ABG — assess ventilatory status
12. Imaging
- First-line: Noncontrast CT head — often normal or may show hyperdense basilar artery sign; CT has poor sensitivity for early brainstem infarction [7][10]
- CT angiography (CTA) of head and neck — essential and urgent to identify basilar artery occlusion; should be obtained emergently in any patient with suspected posterior circulation stroke [10]
- MRI brain with DWI — gold standard for confirming ventral pontine infarction; shows restricted diffusion in the basis pontis. May be falsely negative within the first 48 hours for small brainstem strokes [7][10][13]
- MRA — can delineate vertebrobasilar anatomy and residual flow
- Key imaging findings: Bilateral ventral pontine infarction with tegmental sparing; 80% of long-lasting LIS patients have additional lesions outside the brainstem [18]
- CT perfusion may help assess salvageable tissue in the posterior circulation
13. Special Tests
- Coma Recovery Scale–Revised (CRS-R): Validated tool to distinguish LIS from disorders of consciousness; detects subtle signs of consciousness missed by standard exam [19]
- EEG: Often normal or near-normal in LIS (reactive alpha rhythm), in contrast to the diffuse slowing seen in vegetative state — though EEG alone does not reliably distinguish the two [13-14]
- Somatosensory evoked potentials (SSEPs): Typically preserved cortical responses in LIS
- PET scan: Shows preserved or near-normal cerebral metabolism in LIS vs. markedly reduced metabolism in vegetative state [13]
- Event-related potentials (P300): Preserved in LIS, supporting intact cognitive processing [23]
- Brain-computer interfaces (BCI): For complete LIS where even eye movements are lost; fully implantable BCIs have enabled home communication [21]
14. ECG
- Obtain 12-lead ECG to evaluate for:
- Atrial fibrillation — most common cardioembolic source
- Other arrhythmias (atrial flutter, sick sinus syndrome)
- Acute MI (concurrent cardiac event or Takotsubo cardiomyopathy from acute neurological injury)
- Continuous telemetry monitoring in the ICU
- Consider prolonged cardiac monitoring (Holter or implantable loop recorder) for cryptogenic stroke workup
15. Assessment
- Classification: [1][14]
- Classic LIS: Quadriplegia, anarthria, preserved vertical gaze and blinking
- Incomplete LIS: Some voluntary movements beyond eye movements (often distal limb movements)
- Total (complete) LIS: Complete immobility including loss of all eye movements — diagnosis requires neuroimaging (fMRI, BCI) [1]
- Severity stratification: Patients with isolated pontine lesions have better prognosis for emergence from LIS than those with additional extra-brainstem lesions [18]
- Typical presentation: Mean age ~46–56 years; stroke is the cause in ~86% of cases; diagnosis is frequently delayed (mean ~79 days) [4][18]
- Complications: Aspiration pneumonia (major predictor of poor outcome), DVT/PE, pressure ulcers, contractures, UTI, orthostatic hypotension, depression [2][11]
16. Treatment Plan
Acute stabilization
- Airway protection — early intubation for respiratory failure; most patients require mechanical ventilation initially [2]
- Activate stroke code — LIS from basilar artery occlusion is a stroke emergency
- IV tPA if within 4.5 hours of symptom onset [5]
- Endovascular thrombectomy for basilar artery occlusion — now supported by ATTENTION and BAOCHE trials showing superiority over medical therapy (mRS 0–3: 46% vs. 23% with EVT in ATTENTION) [9][11][24]
- ICU admission with continuous monitoring
- Blood pressure management per acute stroke guidelines
- Anxiolytic therapy — patients are fully conscious and aware; address emotional distress [13]
Subacute/rehabilitation
- Early intensive multidisciplinary rehabilitation (within ~1 month) improves functional recovery and reduces mortality [15]
- Tracheostomy and ventilator weaning protocols [2]
- Swallowing rehabilitation — 42% may recover swallow function [15]
- Communication systems: alphabet boards, eye-tracking devices, brain-computer interfaces [2][21]
- Physical therapy: upright tolerance training, distal motor control, wheelchair fitting [2]
- Bowel and bladder management programs [2]
- Eye care (lubricating drops, taping) for corneal protection [2]
Long-term
- 3-year survival rate is 87%; 5-year survival is ~81% with adequate supportive care [16][18]
- Most patients achieve some motor improvement; full motor recovery is rare (3 of 51 in one cohort) [18]
- Quality of life is often rated higher by patients than by their healthcare providers [8]
- Computer-based communication and social connectivity are essential for quality of life [2][16]
17. Disposition
- Admission: All patients with acute LIS require ICU admission for airway management, hemodynamic monitoring, and acute stroke treatment [2-3]
- Transfer: If presenting to a community hospital without neurointerventional capability, emergent transfer to a comprehensive stroke center for EVT [3][24]
- Rehabilitation: Early transfer to a specialized rehabilitation facility with experience in LIS management once medically stable [2][15]
- Specialist consultation: Neurology (stroke), neurointerventional radiology, pulmonology, physiatry, speech-language pathology, ophthalmology, psychiatry [2]
- Long-term care: Most chronic LIS patients are cared for at home with caregiver support; some require long-term skilled nursing [16]
18. Follow Up / Return Precautions
- Recovery timeline: Most emergence from LIS occurs within the first 2 years; functional recovery is generally better in nonvascular etiologies and in those surviving beyond 4 months [18][25]
- Follow-up: Regular neurology follow-up for secondary stroke prevention, rehabilitation progress, and communication technology optimization
- Secondary prevention: Antiplatelet or anticoagulation therapy based on stroke etiology; statin therapy; aggressive vascular risk factor management [7]
- Caregiver support: Emotional stress on caregivers is a key long-term issue; connect families with support organizations (e.g., ALIS — Association du Locked-In Syndrome) [4][16]
- Return precautions for caregivers: Seek immediate medical attention for fever (aspiration pneumonia), respiratory distress, new neurological changes, skin breakdown, or signs of DVT/PE
- Patient counseling: Despite severe disability, patients with LIS often report meaningful quality of life; 47.5% report good mood, 61% report sexual desire, and 81% meet with friends regularly [4]
Images
References
1. Therapeutic Interventions in Patients With Prolonged Disorders of Consciousness. — Thibaut A, Schiff N, Giacino J, Laureys S, Gosseries O. The Lancet. Neurology. 2019.
2. Locked-in Syndrome: Practical Rehabilitation Management. — Farr E, Altonji K, Harvey RL. PM & R : The Journal of Injury, Function, and Rehabilitation. 2021.
3. Locked-in Syndrome: A Critical and Time-Dependent Diagnosis. — Barbic D, Levine Z, Tampieri D, Teitelbau J. Cjem. 2012.
4. The Locked-in Syndrome: A Syndrome Looking for a Therapy. — León-Carrión J, van Eeckhout P, Domínguez-Morales Mdel R, Pérez-Santamaría FJ. Brain Injury. 2002.
5. Locked-in Syndrome Responding to Thrombolytic Therapy. — Johnson TM, Romero CS, Smith AT. The American Journal of Emergency Medicine. 2018.
6. Vertebrobasilar Disease. — Savitz SI, Caplan LR. The New England Journal of Medicine. 2005.
7. Posterior Circulation Ischaemic Stroke and Transient Ischaemic Attack: Diagnosis, Investigation, and Secondary Prevention. — Markus HS, van der Worp HB, Rothwell PM. The Lancet. Neurology. 2013.
8. Basilar Artery Occlusion. — Mattle HP, Arnold M, Lindsberg PJ, Schonewille WJ, Schroth G. The Lancet. Neurology. 2011.
9. Endovascular Management of Acute Stroke. — Nguyen TN, Abdalkader M, Fischer U, et al. Lancet. 2024.
10. Diagnosis of Reversible Causes of Coma. — Edlow JA, Rabinstein A, Traub SJ, Wijdicks EF. Lancet. 2014.
11. Locked-in Syndrome Responding to Endovascular Treatment. — Song J, Huang J, Li L, et al. Journal of Neurointerventional Surgery. 2023.
12. Diagnosis and Management of Transient Ischemic Attack and Acute Ischemic Stroke: A Review. — Mendelson SJ, Prabhakaran S. The Journal of the American Medical Association. 2021.
13. Brain Function in Coma, Vegetative State, and Related Disorders. — Laureys S, Owen AM, Schiff ND. The Lancet. Neurology. 2004.
14. Chronic Disorders of Consciousness. — Bernat JL. Lancet. 2006.
15. Locked-in Syndrome: Improvement in the Prognosis After an Early Intensive Multidisciplinary Rehabilitation. — Casanova E, Lazzari RE, Lotta S, Mazzucchi A. Archives of Physical Medicine and Rehabilitation. 2003.
16. Long-Term Survival, Prognosis, and Life-Care Planning for 29 Patients With Chronic Locked-in Syndrome. — Katz RT, Haig AJ, Clark BB, DiPaola RJ. Archives of Physical Medicine and Rehabilitation. 1992.
17. The Etiology of Posterior Circulation Infarcts: A Prospective Study Using Magnetic Resonance Imaging and Magnetic Resonance Angiography. — Bogousslavsky J, Regli F, Maeder P, Meuli R, Nader J. Neurology. 1993.
18. Demographic, Medical, and Clinical Characteristics of a Population-Based Sample of Patients With Long-Lasting Locked-in Syndrome. — Nilsen HW, Martinsen ACT, Johansen I, et al. Neurology. 2023.
19. Coma Prognostication After Acute Brain Injury: A Review. — Fischer D, Edlow BL. JAMA Neurology. 2024.
20. Approach to the Patient in Vegetative State. Part II: Differential Diagnosis. — Latronico N, Antonini L, Taricco M, Vignolo LA, Candiani A. Minerva Anestesiologica. 2000.
21. Fully Implanted Brain–Computer Interface in a Locked-In Patient with ALS. — Vansteensel MJ, Pels EGM, Bleichner MG, et al. The New England Journal of Medicine. 2016.
22. Acute Ischemic Stroke. — Powers WJ. The New England Journal of Medicine. 2020.
23. Brain Response to One's Own Name in Vegetative State, Minimally Conscious State, and Locked-in Syndrome. — Perrin F, Schnakers C, Schabus M, et al. Archives of Neurology. 2006.
24. Focused Update to Guidelines for Endovascular Therapy for Emergent Large Vessel Occlusion: Basilar Artery Occlusion Patients. — Heit JJ, Chaudhary N, Mascitelli JR, et al. Journal of Neurointerventional Surgery. 2024.
25. Locked-in Syndrome: A Review of 139 Cases. — Patterson JR, Grabois M. Stroke. 1986.