Nerve Problems in Your Forearms: Understanding AIN Syndrome

Do you experience pain in your forearm that comes and goes or weakness in your thumb and index finger? You could have a condition called anterior interosseous nerve (AIN) syndrome, a rare type of neuropathy. 

Getting an accurate diagnosis of AIN syndrome is key, as without treatment, your symptoms may become permanent. At Anthony Echo, MD, with multiple offices in Houston, Texas, our nerve specialist diagnoses and treats this debilitating condition.

Keep reading to learn what you need to know about AIN syndrome and how Dr. Echo and our team can help you regain normal function.

What is AIN syndrome?

You have a large nerve that runs from your shoulder to your elbow, where it branches off and continues to run to your wrist and fingers. It’s called the median nerve. 

The branch of this nerve that works most of the muscles of your forearm and some of your fingers is called the anterior interosseous nerve. When this nerve gets damaged or inflamed from injury or overuse, for example, you can develop AIN syndrome, sometimes called Kiloh-Nevin syndrome. 

Compression or entrapment of this nerve may also trigger AIN syndrome. However, recent research indicates the condition may be a type of neuralgic amyotrophy, a disorder of the peripheral nervous system.

Symptoms of AIN syndrome

AIN syndrome may share symptoms with other conditions, like carpal tunnel syndrome (CTS), so it’s important to seek medical help if you have any of these symptoms. Symptoms that may indicate you have AIN syndrome include:

• Pain the forearm that may come and go (transient pain)
• Transient pain in the wrist or elbow
• Weakness in the thumb and index finger 

The main difference between CTS and AIN syndrome is that CTS typically causes tingling and numbness, whereas AIN syndrome only affects motor nerves and doesn’t produce any sensory problems. 

To diagnose your condition, Dr. Echo reviews your symptoms and medical history and performs a physical evaluation. He may ask you to make an “okay” sign with your thumb and forefinger or hold a sheet of paper between those fingers to check your muscle strength. If you have AIN syndrome, you won’t be able to perform these tasks.

Is AIN syndrome treatable?

The good news is that in most cases Dr. Echo can treat your AIN syndrome, alleviating your pain and restoring function to your fingers. However, it’s important to seek early treatment since your symptoms may become permanent if not addressed. 

Non-invasive treatments

Once diagnosed, most patients with AIN syndrome respond well to nonoperative treatment modalities. Before recommending surgery, Dr. Echo may recommend:

• Resting the affected arm
• Splinting or bracing (usually near 90 degrees at the elbow)
• Nonsteroidal anti-inflammatory drugs (e.g., ibuprofen)
• Physical therapy
• Therapeutic massage

Most patients improve within 6-12 weeks after starting these noninvasive treatments. 

Surgical decompression

If Dr. Echo believes your symptoms are caused by nerve compression, or if your symptoms are severe, he may recommend surgical treatment. During this procedure, Dr. Echo decompresses the nerve by releasing structures that entrap the nerve and/or clearing any extraneous tissue to alleviate pressure. 

To learn more about AIN syndrome or to set up a consultation, schedule an appointment at the Anthony Echo, MD, office in Houston, Texas, nearest you.