Hemicrania Contínua - An Overview

Introduction

It is a syndrome characterized by moderate but continuous headaches on one side of the head. It is a primary headache, which means it is the main condition and not a symptom of an underlying condition.

It is a rare condition, but the rarity is thought to be due to the underdiagnosis of the condition. HC is relatively featureless, but when it is exacerbated, it mimics symptoms similar to a migraine (intense headache, nausea, vomiting, increased sensitivity to light and sound, etc.

The International Classification of Headache Disorders (ICHD-3) has placed HC under the trigeminal autonomic cephalgias (TACs)- which are a group of primary headache disorders characterized by unilateral pain that occurs in association with generally prominent ipsilateral (same side) cranial autonomic features.

The cranial autonomic features include-

1. Ptosis- Drooping of the upper eyelid.

2. Lacrimation- Secretion of the tears.

3. Rhinorrhea- Discharge of thin clear fluid.

4. Facial Swelling- Typically seen on the affected side.

5. Conjunctival Injection- Enlargement of the blood vessels that supply the conjunctiva (thin clear membrane of the eye).

6. Pupil Changes- This includes changes in the dynamic and static pupillary responses typically seen in autonomic neuropathy.

A few other types of primary headaches that come under TCAs are-

1. Cluster Headache (CH)- It is a unilateral headache that occurs in groups or clusters separated by pain-free periods.

2. Paroxysmal Hemicrania (PH)- Also known as Sjaastad syndrome, it is a recurrent one-sided headache; the affected individuals experience throbbing, claw-like, or boring pain on one side of the face, in and around or behind the eye; and occasionally reaching the back of the neck.

3. Short-Lasting Unilateral Neuralgiform Headache Attacks With Cranial Autonomic Symptoms (SUNA)- In this type of TACs, the pain is moderate to severe and occurs around one eye; the duration can range from five seconds to five minutes per episode. Attacks are multiple and occur only as many as 3 to 200 per day. The pain can be burning, stabbing, electric, or throbbing in nature. Along with pain, SUNA can present with any of the cranial autonomic features mentioned above.

4. Short-Lasting Unilateral Neuralgiform Headache Attacks With Conjunctival Injection and Tearing (SUNCT)- The condition is similar to SUNA, but the SUNCT syndrome involves only two autonomic features- Conjunctival injection and tearing. HC mimics almost all of the conditions mentioned above, but the pathognomic and diagnostic feature that separates HC from other TACs is its ability to be treated by Indomethacin- which is a non-steroidal anti-inflammatory drug. Besides medical therapy, HC can also be managed with invasive treatments like occipital nerve stimulation (ONS) and deep brain stimulation (DBS).

What Causes Hemicrania Continua?

The exact cause of HC is unknown; in fact, the areas of the affected brain that result in HC have also not been completely understood. However, researchers have observed a few details that explain the disease process to some extent-

1. The pain threshold is reduced in individuals suffering from HC, making them easily susceptible to pain.

2. The areas of the brain that get activated when subjected to a positron emission tomographic (PET) scan indicating their involvement in HC are-

• Hypothalamus- It is a region in the ventral brain that coordinates the endocrine system.

• Pons- The part of the central nervous system that connects the medulla (bottom part of the brain) with the cerebellum (a portion of the brain in the back of the head).

• Midbrain- It is the connection central between the brain and the spinal cord.

Now what triggers the activation of these areas is yet to be determined, but so far, it is absolute that HC is a brain disorder, and its pathophysiology (process associated with the disease) bears similarity with other primary headaches.

What Are the Symptoms Of Hemicrania Continua?

They are as follows-

1. It presents as a unilateral, continuous headache without side shift.

2. The pain is mostly in the anterior area of the head, and it is typically mild to moderate in nature.

3. The quality of the pain can be described as dull, aching, or pressing and generally lacking associated features.

4. In the majority of the patients, exacerbations (worsening) of severe pain are superimposed on the continuous baseline pain. These exacerbations can last from 20 min to several days and may be accompanied by autonomic features like conjunctival injection and lacrimation.

5. Other symptoms include photophobia (sensitivity to light), phonophobia (sensitivity to sound), nausea, and vomiting.

How Is Hemicrania Continua Diagnosed?

The international headache criteria for HC are-

• Headache for more than three months, along with the criteria mentioned under the subheadings B and D.

• HC should have all the characteristics mentioned below-

  • Unilateral pain without side shift.

  • The pain should occur on a daily basis and it should be continuous in nature, without pain-free intervals.

  • The pain should be of moderate intensity, which can occasionally become severe.

• HC should have at least one of the below-mentioned autonomic features-

  • Conjunctival injection and/or lacrimation.

  • Nasal congestion and/or rhinorrhea.

  • Ptosis and/or miosis.

• A complete response to therapeutic doses of Indomethacin.
• Not attributed to any other disorder.

If the headache fulfills the above-mentioned criteria, it can be diagnosed as HC.

How Is Hemicrania Continua Treated?

The treatment of HC is prophylactic and is done with a non-steroidal anti-inflammatory (NSAID) drug called Indomethacin. The typical dose ranges from 25 mg- 300 mg daily, which may be adjusted depending on clinical fluctuations.

Concurrent treatment with mucosa protective agents should be considered, as patients are expected to require long-term treatment. NSAIDs other than Indomethacin are generally of little or no benefit, although a few cases have been reported to respond to Ibuprofen, Piroxicam beta-cyclodextrin, Naproxen, Aspirin, COX-2 inhibitor Rofecoxib, and paracetamol with caffeine. Corticosteroids may be transiently effective.

When all of the non-invasive interventions fail, the healthcare provider will suggest invasive treatments, which include either the administration of Botulinum toxin-A or neurostimulation. Neurostimulation is the process of providing electrical stimulation to the nerves to relieve intractable pain or relieve tremors.

The frequently performed neurostimulations in HC are occipital nerve (nerves that arise from the cervical spine C2 and C3) stimulation (ONS), sphenopalatine ganglion (contains the largest collection of neurons in outside the brain) stimulation (SPG), and deep brain stimulation (DPS).

Conclusion:

In spite of the many treatment options available, the pain experienced in HC is intense, and the affected patients have known to suffer from depression and suicidal tendencies. Because of this, it is important to manage an individual with HC with an interdisciplinary team comprising of neurologists, psychiatrists, physiatrists, etc.