Despite being a diagnosis little known to general physicians, paresthetic notalgia is a frequent complaint in dermatology clinic. The correlation with degenerative changes in the thoracic spine is somewhat known, but the electrophysiological study in these cases is still unfamiliar to the neurophysiologist. The objective of this paper is to present a clinical case, describe and discuss the neurophysiological evaluation of a patient with paresthetic notalgia.
Paresthetic Notalgia (PN) is a frequent reason for searching a dermatology clinic. Due to the correlation of PN with degenerative changes of the thoracic spine, neurophysiological evaluation has been requested, but it is still an unusual entity for the neurophysiologist. Paresthetic notalgia has been referred as: “dorsal pruritus with hyperpigmentation”, “pruriginous dorsal melanosis”, “Pierini and Borda melanocytic pruritus” , “localized hereditary pruritus”, “pigmented posterior pruritic spot” and “pruritus subscapular”[1,2]. For a long period it was considered as one of the clinical varieties of primary cutaneous amyloidosis receiving the name “dorsal amyloid lichen”. It is now known that the presence of amyloid substance is a consequence of pruritus and itching [1,3]. Paresthetic Notalgia is considered as a chronic sensory neuropathy affecting in particular the interscapular region between T2 to T6 levels, uni- or bilateral, and may present a wider distribution [1,2].
A 47-year-old female patient, who reported dark spots on the upper dorsal region in both sides and on the lower right dorsal region, accompanied by intense local pruritus, with a five-year evolution. Background: chronic back pain and low back pain for 16 years.
The dermatological examination showed hyperchromic macules in the upper dorsal region bilaterally and the lower dorsal region on the right side, Figure 1. Normal nerve palpation; deep reflexes normal and symmetric; sensory mapping: tactile, termal and pain sensory modalities preserved, Figure 2. Image
examination: X-ray shows mild left dorsal scoliosis, without significant kyphosis, Figure 3.
In neurophysiological approach the Electromyography
(EMG) was the technique chosen to evaluate the dorsal roots
because its has high sensitivity, specificity and reproducibility in
radiculopathies . The EMG showed mild chronic neurogenic
motor pattern in dorsal paravertebral muscles of T3-T4 to T8-
T10 bilaterally and at the T8 and T9 level on the right side. In
T5 level on the right, side increased jitter was recorded during
single fiber EMG study, characterizing a chronic denervation and
reinnervation process, with constant remodeling of the motor
units , Figure 4. In T8 level, in the left side, pseudomyotonia
was found during spontaneous activities analyses, a feature of
axonal motor hyperexcitability, Figure 5.
In spite of being considered a sensory neuropathy [1,2], in
the this case of PN no sensory loss was found, tactile, thermal
and painful sensitivity in the involved territory associated with
Aβ, Aδ and C fibers was normal. However, the motor evaluation
showed root involvement in the symptomatic area. According to
the literature, pruritus would be mediated by C fibers, similar to
neuropathic pain, but due to the sustained hyperexcitability of
these fibers due to itching and to a lesser extent by posttraumatic
neuroplasticity . These findings related to motor fibers
in dorsal roots would reflect a picture of global intraneural
hyperexcitability of the axons also involving nociceptive
C-related fibers related to pruritus, as postulated about A-wave
and pain in a previous papper .