Neuropathic Itch

1. NEUROPATHIC
ITCH
A D E W I J AYA , M D
J A N U A R Y 2 0 1 9

2. ITCH
• A distinct sensation that provokes the desire to scratch
• C-fiber and A fibers
• Itch-selective primary afferents (histamine)

3. SPINAL CIRCUIT OF ITCH
• The primary afferents that convey pruriception from the periphery to the spinal cord
target the superficial dorsal horn (lamina I and the outer region of lamina II)
• Several cell types in the dorsal horn are believed to be involved in mediating
pruriception, including the neurons that express gastrin releasing peptide (GRP) and
those that express its receptor (GRPR).
• The neurons that convey pruriception from the spinal cord to the brain are a subset of
anterolateral tract neurons, which target numerous brain structures including the
rostral ventral medulla, the parabrachial nucleus, the cerebellum, and the thalamus.

4. SPINAL CIRCUIT OF ITCH
• Selective modulation of itch and pain by mu opioids is likely to occur at the level of the
spinal cord rather than the brain
• Morphine was found to decrease the activity of trigeminothalamic neurons that
seemed to be tuned for nociception while increasing the activity in those that seemed
tuned for pruritoception
• Spinal cord integration of sensory input is sufficient for the basic decoding of itch vs
pain

6. Dermatological Systemic
Psychological Neuropathic
ITCH

7. NEUROPATHIC ITCH
• 8% to 19% of patients affected by chronic pruritus
• Severe
• Peripheral nervous system

11. TREATMENT

12. SUMMARY
• Neuropathic itch is any injury or dysfunction along the afferent itch pathway that
results in a sensation to scratch.
• Diagnosing chronic itch is challenging and NI should be considered after ruling out
dermatological and systemic causes.
• Numerous neuropathic itch syndromes, affecting the peripheral and central nervous
systems, exist and should be recognized by clinicians.
• Treatment is challenging and requires tailoring therapies. The most common
treatments are GABAnergic anticonvulsant medications and topical anesthetics
• Affect QOL

13. REFERENCES:
• Steinhoff M, Schmelz M, Szabó IL, Oaklander AL. Clinical presentation, management,
and pathophysiology of neuropathic itch. The Lancet Neurology. 2018 Aug 1;17(8):709-
20.
• Rosen JD, Fostini AC, Yosipovitch G. Diagnosis and Management of Neuropathic Itch.
Dermatologic clinics. 2018 Apr 26.
• Hachisuka J, Chiang MC, Ross SE. Itch and neuropathic itch. Pain. 2018 Mar
1;159(3):603-9.