Beyond the Rash : The Lingering Sting of PHN

Understanding PHN : 

Post herpetic neuralgia (PHN)  is a chronic pain condition affecting nerves , which commonly develops as a reinfection after shingles. The Varicella zoster virus that is known to cause shingles , stays in the nerve root for over periods . Now , this virus gets triggered sometimes from various trigger factors and when this happens it affects the nerve as herpetic neuralgia .

What are all the trigger factors?

The exact mechanism behind the cause of neuralgia is not fully understood but it is believed to be exacerbated by 

1. Touch or pressure - Over the nerve affected 
2. Exposure to extreme temperatures 
3. Stress, anxiety or emotional distress 
4. Sensory stimulus 
5. Fever 
6. Physical activity 
7. Hormonal changes 
8. Nerve damage
9. Other medical conditions like thyroid disorders and chronic fatigue syndrome.

These are some of the trigger factors whereas "trigger zone" is an area near the affected nerve where low intensity mechanical stimulation (such as light touch , an air puff or even hair -bending ) can elicit a typical pain attack . The location of trigger zome depends on which division of nerve is involved 

Symptoms of PHN 

• Rashes along the course of nerve root which is one of the unique feature for herpetic neuralgia 
• Sharp , shooting, lancinating pain which is elicited by slight touch over the trigger zones 
• The pain occurs between a period of latency and refractory period .
• Numbness or tingling 
• Burning or aching sensation 
• Facial pain 
• Sleep disturbances 

Diagnosis and investigation :

• Proper chairside investigation 
• Trigger zone examination 
• Diagnostic nerve blocking 
• Advanced investigation like PET scan , functional MRI

Management : 

• Pharmacological approach 
• Surgical approach 
• Lifestyle modifications 
• Stress reduction protocol

PHN can be a life threatening condition but with proper treatment it can be reversed but the progress is very slow .