Lateral Intermuscular Septum Syndrome
RADIAL NERVE
Recognising the Symptoms and Solutions
Ali Phillips | Hand & Wrist Specialist
Aching arm and weak wrist?
I'm Ali Phillips. If you're experiencing a persistent, deep ache in your upper arm combined with wrist weakness, you might be dealing with **Lateral Intermuscular Septum Syndrome**. It’s a specific type of nerve compression that is often overlooked. For this reason, my goal is to provide clear, expert information to help you understand this condition and the effective treatments available.
Book a ConsultationWhat is Lateral Intermuscular Septum Syndrome?
Lateral Intermuscular Septum (LIS) Syndrome is a nerve compression condition affecting the radial nerve in the upper arm. The radial nerve travels down your arm and is responsible for straightening your wrist and fingers. On its journey, it passes through a fibrous tunnel called the lateral intermuscular septum.
In Lateral Intermuscular Septum Syndrome, this septum becomes too tight, squeezing the radial nerve. This is similar to, but higher up than, the more commonly known Radial Tunnel Syndrome. Consequently, the compression irritates the nerve, leading to a distinct set of symptoms like pain in the upper arm and weakness in the wrist.
What are the Symptoms of Lateral Intermuscular Septum Syndrome?
Deep Arm Pain
A persistent, aching pain on the outer side of your upper arm, between the biceps and triceps muscles.
Wrist Weakness
Noticeable weakness when trying to extend (lift) your wrist and fingers, affecting your grip and daily tasks.
Numbness or Tingling
Sometimes, sensory changes like numbness can occur on the back of the hand, though pain and weakness are more common.
Tired of Unexplained Arm Pain?
If these symptoms sound familiar and you haven't found a solution, it's time for a specialist evaluation. An accurate diagnosis is the first step towards effective treatment for Lateral Intermuscular Septum Syndrome.
Find Out What's Going OnHow I Diagnose Lateral Intermuscular Septum Syndrome
Lateral Intermuscular Septum Syndrome is a clinical diagnosis, meaning it's identified through a specific set of physical exam findings. Specifically, I look for a classic "tetrad" of four key signs:
1️⃣
Tenderness over the lateral intermuscular septum in the upper arm.
2️⃣
Weak Wrist Extension that is different from your other side.
3️⃣
Positive Scratch Collapse Test, a specific nerve test that indicates irritation at the LIS.
4️⃣
Positive Response to Taping, where applying Kinesio-tape provides immediate, temporary relief of symptoms.
When all four of these signs are present, it gives us a confident diagnosis and points us directly towards the most effective treatment plan.
How can we get you better?
My treatment approach is stepwise, always beginning with the least invasive options. Surgery is only considered if conservative measures fail to resolve your Lateral Intermuscular Septum Syndrome.
Kinesio-Taping (First-Line Treatment) My primary treatment is the application of Kinesio-tape over the LIS. This special tape gently lifts the skin and underlying tissues, which can immediately reduce pressure on the radial nerve and provide significant symptom relief. Its effectiveness is also a key part of the diagnosis.
Activity Modification & Therapy In addition, we will identify and avoid activities that aggravate your symptoms. A hand therapist can provide exercises to improve nerve gliding and strengthen supporting muscles without causing further irritation.
Injections In some cases, an ultrasound-guided injection of local anaesthetic or corticosteroid can help confirm the diagnosis and provide temporary relief from inflammation.
Surgery is reserved for cases where non-surgical treatments have not provided lasting relief and symptoms continue to impact your quality of life.
What it is: This is an open procedure where I make a carefully planned incision on the outer side of the upper arm. I use ultrasound to pinpoint the exact location of the compression to keep the incision as small as possible. I then directly visualise the radial nerve and carefully release the tight, fibrous bands of the lateral intermuscular septum, giving the nerve more space.
Benefits
- Directly and permanently relieves the pressure on the radial nerve
- High success rate for relieving pain and restoring strength
Your Options: The decision to have surgery is a significant one. We will make this decision together after thoroughly exploring all other options. Your choices always include:
- No Treatment: You can choose to manage the symptoms without intervention, though this may limit your activities.
- Continued Non-Surgical Management: We can continue with taping, therapy, and activity modification if they provide adequate relief.
- Surgical Decompression: To provide a definitive solution for the nerve compression.
Risks & Complications of Surgery
It is crucial to have realistic expectations. While surgery is generally very successful, all procedures have risks. Based on peer-reviewed literature, here are the potential complications:
- Persistent Symptoms (Failure to Improve): In a small number of cases (around 5-10%), some pain or weakness may persist even after surgery.
- Nerve Injury: The radial nerve is delicate. The risk of a permanent, significant injury to the nerve during surgery is very low (less than 1%), but temporary bruising or irritation can occur, leading to temporary numbness or weakness.
- Infection: The risk of a wound infection is low, approximately 1-2%.
- Scarring: You will have a permanent scar. Some people may develop a thickened (hypertrophic) or sensitive scar.
- Complex Regional Pain Syndrome (CRPS): A rare but serious complication causing severe pain, swelling, and stiffness. The risk is less than 1%.
Frequently Asked Questions about Lateral Intermuscular Septum Syndrome
They are both compressions of the radial nerve, but at different locations. LIS Syndrome occurs higher up in the upper arm, in the lateral intermuscular septum. In contrast, Radial Tunnel Syndrome occurs lower down in the forearm, where the nerve passes through a tunnel of muscles.
It can be caused by a direct injury or fracture, repetitive overuse from sports or work (like throwing or using certain tools), or even from significant muscle growth in athletes or bodybuilders which crowds the nerve.
The elastic properties of Kinesio-tape create a gentle, lifting effect on the skin and the layers of tissue beneath it. Ultimately, this microscopic lifting can decompress the area around the lateral intermuscular septum, giving the radial nerve more space and reducing irritation, which is why it provides such immediate feedback.
Usually, no. LIS Syndrome is primarily a clinical diagnosis based on the tetrad of signs found during the physical exam. Furthermore, nerve conduction studies are often normal in compression syndromes without significant nerve damage, so they are not typically required to make the diagnosis.
More About Recovery and LIS Syndrome
Recovery is relatively quick. You will have a dressing and need to keep the wound clean and dry. Light activities can be resumed almost immediately. However, strenuous activity and heavy lifting should be avoided for 4-6 weeks to allow the tissues to heal fully. Most people find their pain and weakness improve significantly within the first few weeks.
No, the weakness is caused by the nerve being irritated. Once the compression is relieved, either with taping or surgery, the nerve can function normally again and strength typically returns fully.
Recurrence after a complete surgical release is very rare. The procedure is designed to permanently open up the space for the nerve, providing a long-lasting solution.
While the pain can be in a similar area, they are different conditions. Tennis elbow (lateral epicondylitis) is a tendon problem at the elbow. In contrast, LIS Syndrome is a nerve problem higher up in the arm. It's important to get the right diagnosis as the treatments are very different.
LIS Syndrome is a relatively newly described condition and is less common than other nerve compressions. Therefore, it requires a specialist who is familiar with the specific diagnostic tests to identify it correctly, which is why it can sometimes be missed or misdiagnosed. For more information, you can read studies on the topic, like this one from the Journal of Hand Surgery.
While not always necessary for diagnosis, an ultrasound can be very helpful. For instance, I use it to visualise the nerve and confirm the exact point of compression, which helps guide injections and plan the precise location for a surgical incision if needed.
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