How Is Grip Strength Used to Monitor MMN Progression?

If you have Multifocal Motor Neuropathy (MMN), you are likely familiar with the routine of squeezing a handheld device as hard as you can during your neurology appointments. Neurologists measure your grip strength because it provides an objective, measurable number that tracks how well your hand and arm muscles are working ^[1].

While it is only one piece of a broader assessment, this simple test is a useful tool to help your care team evaluate how you are responding to Intravenous Immunoglobulin (IVIg) treatment and whether your disease is stable ^[1].

How Grip Strength is Measured

To get an accurate number, neurologists use specialized medical devices called dynamometers. The two most common types used for MMN are:

• Jamar dynamometer: A rigid handle that measures force when you squeeze it.
• Martin Vigorimeter: A device with a rubber bulb that measures pressure when squeezed.

Research shows that both devices are highly reliable and their measurements correlate strongly with one another ^[2]. In studies, patients often prefer the Vigorimeter ^[2].

However, readings from a Jamar device cannot be directly swapped with readings from a Vigorimeter. To accurately track your progress, your neurologist needs to test you the same way every time ^[2]. For your results to be meaningful, your care team should ideally use the same device, the same hand, the same posture, and the same number of squeeze attempts at every visit.

What Can Affect Your Reading?

Your grip strength is not a perfect, unchanging number. It can be temporarily influenced by several daily factors, including:

• General fatigue or recent strenuous activity
• Pain in your hands or joints
• How much effort you are able to exert in that exact moment
• The temperature of the room or your hands
• Where you are in your dosing interval (the time between your scheduled IVIg infusions)

Tracking IVIg Effectiveness and “Wear-Off”

One of the main challenges with IVIg therapy is finding the right dose and the right schedule for your specific body. Grip strength gives your doctor numerical data to help guide these decisions.

For example, your doctor can use these measurements to see if the IVIg is wearing off before your next infusion. If your grip strength is consistently lower and your symptoms are worse right before your next scheduled treatment, it may indicate that your dosing interval is too long. Some research models suggest that more frequent dosing intervals can produce a more consistent grip strength response, preventing that end-of-cycle weakness ^[3]. Do not alter your dose or schedule on your own; your neurologist will look for a reproducible pattern and weigh the benefits and risks of changing your treatment.

When tracking improvements, one specific research model used an increase of about 4 kg (roughly 8.8 lbs) as a benchmark for a “clinically meaningful” improvement in grip strength after starting IVIg ^[4]. However, this is a study-specific research benchmark, not a universal goal or a pass/fail grade for your treatment. The meaning of a change depends heavily on your baseline (your starting strength), the specific device used, and your personal disease progression.

Distinguishing Normal Fluctuations from Disease Progression

Because so many daily factors affect your grip, it is completely normal for your strength to fluctuate slightly from appointment to appointment. If you have a single lower reading, it does not automatically mean your MMN is getting worse.

Studies following MMN patients who are clinically stable on IVIg therapy found that their grip strength measurements naturally fluctuated, sometimes even beyond what researchers consider a significant difference ^[5]. Because a single lower score can just be a normal variation, doctors do not rely on a single drop in grip strength to diagnose disease progression ^[5].

Instead, true disease progression is identified by a sustained decline. Your doctor will look for a pattern of decreasing strength over multiple visits ^[5].

When to Seek Immediate Care: While small fluctuations are normal, sudden or severe changes are not. If you experience rapidly worsening weakness, sudden one-sided weakness, or any trouble breathing or swallowing, seek urgent medical care immediately.

A Multimodal Approach to Monitoring

Grip strength measures only specific hand and arm muscles, and MMN can affect different muscles asymmetrically. Therefore, grip strength cannot by itself establish treatment response or justify changing IVIg ^[1].

Neurologists get the best picture of your health by looking at your grip strength alongside other measures, such as:

• Manual muscle testing: Where the doctor pushes against your arms and legs to test overall strength.
• Functional tests: Timed walking or dexterity tests (like moving pegs on a board).
• Patient-reported questionnaires: Such as the MMN-RODS (Rasch-built Overall Disability Scale for MMN), which asks you to rate your ability to do specific daily activities like opening jars, buttoning clothes, or brushing your teeth ^[6].

By combining objective numbers with your real-world daily function, you and your neurologist can make informed, shared decisions about your MMN care ^{[1] [6]}.