The locked-in syndrome is defined as quadriplegia and anarthria (loss of articulate speech) with the preservation of consciousness (1). It is typically caused by a lesion to the ventral pons, the most common etiology being vascular in nature through basilar artery occlusion or pontine hemorrhage.
Conversion disorder (previously referred to as “hysterical neurosis”) is categorized as a form of somatoform disorder. It is the deficit of voluntary motor or sensory function requiring an extensive work-up to exclude any organic cause. Many different modalities have been used to differentiate organic problems from psychological causes, including electroencephalogram (2), evoked potentials (3–5), magnetic resonance imaging (6), and computed tomography. Due to the varied nature of presentation, no single diagnostic test can be reliably used to differentiate conversion disorder from organic illnesses.
We report a patient who, after implantation of a spinal cord stimulator, manifested locked-in syndrome resulting from a conversion disorder.
A 42-year-old, 127-kg woman, who had undergone multiple spinal surgeries for chronic back and leg pain and implantation of an externally placed spinal cord stimulator, developed an infection at the site of the generator, resulting in removal of the entire system. She subsequently presented for implantation of spinal cord stimulator electrodes via laminectomy at the T10–12 level.
The patient was sedated with midazolam 2 mg and a scopolamine patch placed preoperatively due to a history of postoperative nausea and vomiting. Anesthesia was induced with propofol 220 mg and fentanyl 150 mcg. Tracheal intubation was facilitated with succinylcholine 120 mg. After induction of anesthesia, there was one brief episode of hypotension (70/35 mm Hg). Ephedrine 10 mg was given and her arterial blood pressure increased to 100/50 mm Hg and remained stable throughout the surgery. Anesthesia was maintained with sevoflurane and nitrous oxide. Before skin incision, 1% lidocaine with epinephrine 10 mL was infiltrated subcutaneously, and no local anesthetics were administered before closure. Estimated blood loss was less than 25 mL. Neuromuscular blockade was reversed with neostigmine 3 mg and glycopyrrolate 0.4 mg. The patient was tracheally extubated and transferred to the postanesthetic care unit.
Half an hour after postanesthetic care unit arrival, the patient was noted to be “unresponsive,” with diffuse quadriplegia and lower facial diplegia, but able to open her eyes. Her pupils were equal and reactive to light. She did not respond to painful stimuli via sternal rub and lacked a startle response. She exhibited no gag reflex, but her corneal reflex was intact. Her extremities were flaccid and areflexic. The patient’s vitals were stable and oxygen saturation was 100%. Glucose level was checked and measured as 154. The scopolamine patch was removed and physostigmine 2 mg was given; approximately 3 min later she began retching. However, she still did not respond to painful stimulation. An emergency computerized tomography of the head and spine was performed which did not reveal any intracranial or spinal pathology. At this time, there was no clear organic etiology accounting for her symptoms.
Over the next few hours, the patient gradually started to improve, opening her eyes to verbal stimuli, and blinking appropriately to painful stimuli. She regained the ability to protrude her tongue weakly and open her mouth slightly on command. She remained unable to move her head or shrug her shoulders. A few hours later, she became able to squeeze her right hand with 2/5 strength, but remained hyporeflexic and flaccid.
Approximately 7 h later, her upper extremity strength improved as she was able to grab the guard rail. She was able to communicate through simple commands by blinking her eyes (once for yes, twice for no) and reported pain accordingly. Hydromorphone was given with good pain control per patient report. Two hours after being given hydromorphone, the patient was able to ring the call bell and spoke hoarsely but understandably, reporting a sore throat and back pain. She was now able to lift her leg.
The next day, neurologic examination revealed intact cranial nerves, 3/5 strength in upper and lower extremities, 1+ reflex, and articulate speech. She began to ambulate, and eat and drink. A psychiatry consultation was obtained and during this interview, she denied any active problems, but reported having seen a therapist a few years previously. The patient reported a history of some self-injurious behavior (scars on her arms), childhood sexual abuse, and significant alcohol abuse. She reported working in the health care field as a nurse’s aid. Her speech was coherent with no loose associations or formal thought disorder, and she described her mood as “just what you would think for anyone who has been through what I have been through.” The patient met a number of characteristics of conversion disorder, including unexplained neurologic deficits, history of working in the health care setting, and a psychiatric history.
The spinal cord stimulator was then activated with significant symptomatic reduction of back pain. The patient was then discharged with full recovery.
Locked-in syndrome can be classified into three categories: Classic: quadriplegia, anarthria, vertical eye movement, and preserved conscious; Incomplete: same features as classic, except with voluntary movements in addition to vertical eye movement; and Total: complete loss of mobility, loss of any form of communication, but preservation of consciousness (7). In general, quadriplegia and anarthria are due to destruction of the corticospinal and corticobulbar pathways. Consciousness remains intact through the preservation of the reticular formation which lies above the midpons. Vertical eye movements remain intact through preservation of the midbrain tectum. A family member is often the first to recognize and report to the care team about the patient’s awareness of their surrounding, leading to the diagnosis of locked-in syndrome. Diagnosis is commonly delayed, with the mean time to diagnosis being more than 70 days, as these patients are thought to be in a persistent vegetative state (8). There have not been any reports of locked-in syndrome type symptoms from conversion disorder postoperatively.
However, transient paralysis without evidence of an organic cause after anesthesia has been reported (9,10). Chhibber and Lustik (9) reported a patient who presented with paralysis of her left leg after successful spinal anesthesia. Her neurological examination revealed absence of voluntary movement, with hyperesthesia and normal deep tendon reflexes of the affected extremity. The patient was discharged with the diagnosis of conversion disorder and later recovered after outpatient psychiatric consultations. Laraki et al. (10) reported a case of bilateral lower extremity paralysis after epidural neurological examination revealed loss of voluntary movement to the lower extremities with absent proprioception, vibratory sensation, and a patchy sensory loss bilaterally. However, all reflexes, anal tone, and the ability to urinate were intact. Likewise, this patient’s symptoms were unexplainable and transient, suggesting a psychological etiology.
Complications of spinal cord stimulation include displacement of electrodes, spinal cord compression, infection, paraplegia (11), and gastrointestinal symptoms (12). There is one case report of conversion disorder after placement of a spinal cord stimulator (13). This patient had undergone a dorsal column cord stimulator at the C2–5 level for treatment of complex regional pain syndrome Type II of the left upper extremity. The patient presented 10 days postoperatively with transient left lower extremity weakness which progressed to a right-sided hemiparesis over the course of 36 h. The patient had recovered significantly 2 h after a neurological consult, and recovered completely the next day. Throughout this patient’s admission, he was found to be indifferent toward his condition and the findings were inconsistent with any organic involvement, leading to the diagnosis of a conversion disorder.
Before considering a psychological cause, such as conversion disorder, all organic causes should be eliminated. Conversion disorder must be differentiated from malingering and factitious disorders. Unlike factitious and malingering, conversion disorders are manifested unconsciously with no evidence of any external gain. The Diagnostic and Statistical Manual for Mental Disorders requires the involvement of one or more symptoms or deficits in voluntary motor or sensory function suggesting a neurological condition: that there be evidence of a psychiatric history, that it not be intentionally produced or feigned, that it cannot be explained by a general medical condition, that it not be due to any substance or as a culturally sanctioned behavior or experience, that it must cause clinically significant distress, that it not be limited to pain or sexual dysfunction, and that it not be accounted for by another mental disorder (14). Conversion disorder tends to occur more commonly in females and those in lower socioeconomic classes. Treatment for conversion disorder is generally supportive with physical therapy and reassurance.
Our patient presented with paralysis, anarthria, and preservation of consciousness. She was able to open her eyes to verbal stimuli, and had preserved eye movement. This was after implantation of a spinal cord stimulator, consistent with symptoms of locked-in syndrome. Several factors were considered, such as prolonged anesthetic effects, inadequate reversal of muscle relaxants, metabolic abnormalities, hypoxia, infection, trauma, hemorrhage, or thrombosis leading to ventral pontine infarct, and hematoma or abscess in the spinal cord.
Although not initially considered, intrathecal infiltration may lead to total spinal anesthesia. This may explain some symptoms present in our patient, such as transient paralysis and areflexia. High blocks are associated with respiratory depression and hemodynamic disturbances, neither of which was present. Furthermore, if the patient had experienced a total spinal affecting her cranial nerves and causing the facial diplegia, it is unlikely that her phrenic nerve would have been spared; the patient’s oxygen saturation remained above 98% throughout her stay in the postanesthesia care unit. Organic causes were excluded before considering a psychological cause. It was later revealed that the patient had a psychiatric history and was involved in the health care setting, consistent with this diagnosis. Being exposed to the health care field has been associated with the diagnosis of conversion disorder; the reason for this linkage, however, is not clear. Interestingly, conversion disorders can be associated with physiological abnormalities. A positron emission tomography study demonstrated an increased activity in the orbitofrontal and cingulated cortex in a patient with a known history of hysterical problems who presented with loss of motor function to the lower extremity (15).
In summary, our patient met the characteristics of locked-in syndrome brought on by a conversion disorder. Psychological processes may have a role in producing somatic symptoms through the unconscious via pathways affected by emotional stressors to inhibit areas involved in motor function. This may explain our patient’s condition. Before considering a psychological cause, all organic factors should be excluded with proper tests and consultations, as conversion disorder is a diagnosis of exclusion.
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