Demyelinating lesions often lead to paroxysmal attacks of motor and/or sensory phenomena. Frequently occurring and triggered by movement or sensory stimuli, short, stereotypic, events characterize these unique symptoms. Although sometimes bothersome or even frightening, to patients, these events do not prove to be a true advancement of disease conditions (such as in multiple sclerosis) or lead to further injury to the central nervous system (CNS).
When a patient has multiple sclerosis, common disease symptoms include sensory symptoms in the upper and lower limbs. These are sometimes on one side of the face and include visual loss or diplopia, acute or subacute motor weakness, limb ataxia and gait disturbances, vertigo, bladder incontinence or retention, acute transverse myelitis, pain, and also a phenomenon known as Lhermitte's sign.
Lhermitte's sign (sometimes also referred to as Lhermitte's phenomenon or barber chair phenomenon) is a transient neurologic symptom which arises in patients in whom develop it as sequelae of their neurologic condition. Specifically, it is described as an unpleasant electrical shock sensation that travels down the back and into the limbs when a patient flexes their neck forward toward their chest. As previously stated, Lhermitte's sign is categorized as one of the pain syndromes of multiple sclerosis. Of note, it is not to be confused with Uhthoff phenomenon, another often-noted condition of multiple sclerosis, which is characterized by heat sensitivity.
The condition is named after a French neurologist and neuropsychiatrist, Jean Lhermitte. Pierre Marie and Chatelin first described the sign in 1917. In patients that do not experience the phenomenon by flexing their neck alone, it can be further elicited by having the healthcare provider tap on the cervical spine while in the flexed position. The sensation of electricity traveling down the spinal column is believed to originate in the posterior columns.
While the condition is undoubtedly most known for its association with patients who have multiple sclerosis, there is a broad range of medical ailments and expected causes which also lead to its occurrence. Some of these include tumors, trauma, cervical disc herniation, spondylosis, myelopathy, vitamin B12, transverse myelitis, Behcet's disease and Arnold-Chiari malformation (or any other condition leading to spinal cord compression in the cervical region). The phenomenon may also appear in cancer patients, during or after high-dose chemotherapy or irradiation of the cervical spine. It is also occasionally reported as a facet of a discontinuation syndrome related to certain medications. Psychotropic medications such as SSRIs and SNRIs, specifically paroxetine and venlafaxine have been shown to have an association. When being on these medications for some length of time, and then suddenly halting to drastically reducing dosages, some patients enforce experiencing symptoms similar to Lhermitte's sign. In dentistry, there have been studies which found Lhermitte's sign associated with nitrous oxide abusers (believed to be tied back to depleting vitamin B12).
There are no available statistics regarding the incidence or prevalence of Lhermitte's sign in today's global population. However, there have been studies which found that, at least regarding the disease entity of multiple sclerosis, 16% of patients reported experiencing the symptom.
Lhermitte's sign is described as a transient sensory symptom. To best understand its underlying pathophysiology (which is theoretical in nature) the sensation that is experienced by patients should be first reviewed. Lhermitte's sign is often explained as an almost painful electric shock radiating down the spinal column, and sometimes into the limbs, upon an individual flexing their neck. While it is most frequently encountered in multiple sclerosis, as previously noted, the symptom can arise in many other conditions of the cervical cord. These conditions including various tumors, vitamin deficiencies, cervical disc herniation, Behçet's disease, postradiation myelopathy, and following trauma. One thing that all of these conditions have in common when associated with the presence of Lhermitte's sign is that the patient is believed to have a lesion of the spinal cord in the cervical region or lower brainstem. These lesions are often compressive in nature, typically of the dorsal columns or the caudal medulla. Of course, demyelination can also play a part, in likely causing an ephaptic transmission of nerve impulses at sites of disease activity.
Neck movements, tiredness, stress, and heat can trigger Lhermitte’s sign. Patients often describe Lhermitte's like an electric shock of pain that runs from the head down to the back, and through the arms and legs. It often happens when they bend their head down and touch their chin to their chest.
There are no laboratory, radiological, or other tests to assess or manage Lhermitte's sign. It is a physical exam finding.
If the discomfort is severe, carbamazepine or gabapentin may be beneficial for some patients.
Regarding SSRI withdrawal symptoms, fluoxetine, given the extended length of its half-life, can be given at a single small dosage, and as a result, avoid Lhermitte's sign and other similar symptoms.
The differential diagnosis of Lhermitte symptom in cancer patients includes tumor progression causing spinal cord compression, as well as other treatment complications. Other causes of spinal cord disease that can result in Lhermitte symptom include demyelinating diseases, vitamin B12 deficiency, and structural abnormalities of the spinal canal.
Lhermitte's sign has been noted as a potential side effect of radiation oncology therapies, specifically as an early delayed radiation injury. These often occur within 4 months of radiation therapy.
Cisplatin or docetaxel neurotoxicity has been tied to Lhermitte's sign.
No active intervention is required by healthcare providers beyond an explanation and reassurance; the syndrome usually resolves spontaneously over a period of months to a year.