The neurologist asks me to bend my head forward and immediately I feel a shock of sensation travel down my arms into my fingers. It’s kind of a vibration, buzzing, or tingling more than a shooting pain. I have just shown a positive L’Hermitte's sign.
The extra buzzing I felt is called a dysesthesia since the unusual sensation was provoked by bending my head forward, in contrast to a paresthesia which describes spontaneous tingling, buzzing, partial numbness, sharp pains, or electrical shocks. I get those too.
Not everybody experiences the L’Hermitte's symptom in the same way. For some patients, it is described as an intense electric shock which feels like you’ve just shoved a finger or toe into an electrical outlet. For some, it may just be a very subtle tingling in the fingers, legs, or toes. Or for others, the wave of sensation can also travel down the truck or upwards to the head.
I have been asked, “Is L’Hermitte's a sign or a symptom?”
The answer is that it can be both. The sudden, temporary shock-like or tingling sensation can be a symptom of multiple sclerosis (or other diseases mentioned below). In MS, the occurrence of the shock-like sensation can be an indicator of cervical lesions or spinal cord damage in the cervical or thoraxic areas. In this way, L’Hermitte's becomes a sign.
“How long does L’Hermitte's last?”
The sensation is usually brief and lasts less than a second. However, several shocks can occur one right after the other and may feel continuous.
“Does L’Hermitte's ever go away?”
It can. Just as other MS symptoms may come and go, L’Hermitte's as a symptom may wax and wane as well. At each visit, my neurologist asks me to bend my head down and then I report what I feel (if anything). Sometimes I feel nothing new happen; sometimes the extra tingling in my hands and legs.
“If I experience L’Hermitte's, does that mean I have MS?”
No. Although this symptom is very common in patients with MS, it is not exclusive to MS. L'Hermitte's can be associated with arthritis, disc compression, cervical spondylosis (degeneration of the disc spaces between the vertebrae), spinal cord tumors, pernicious anemia, inflammation from lupus or Behçet’s disease, and even vitamin B12 deficiency, electrolyte imbalance, or nitrous oxide exposure, among others.
"If I do not experience L’Hermitte's, does that mean I do not have MS?"
No. It is definitely possible to have MS and still never experience the L’Hermitte's sign.
“I get a shocking sensation when I bend my head back or to the side, is this the L’Hermitte's sign?”
What you describe is called a reverse L’Hermitte's sign during which bending your head backwards causes the same type of sudden, short-term waves of “electrical” buzzing sensations. If a shock-like sensation travels up from the feet or up the spine when you bend your head forward, that is called an inverse L’Hermitte's sign. It is much less common and is associated with nitrous oxide inhalation.