HomeAnswersNeurologymuscle atrophyCan motor neuron disease only affect the extensor functions and not flexion function?

What could be the adequate diagnosis for muscle weakness and atrophy of the upper extremities?

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Published At October 21, 2022
Reviewed AtOctober 31, 2022

Patient's Query

Hello doctor,

I am a 58-years-old male with atrophy and muscle weakness in the upper extremities for the past 17 years. Muscle weakness only affects the extension functions, not the flexion functions. I underwent a PET scan, EMG, and NCV, and the doctor diagnosed it as multifactor motor neuropathy or motor neuron disease. However, I am not satisfied and need an adequate diagnosis.

Thank you.

Hi,

Welcome to icliniq.com.

I understand your concern.

I have a few questions so that I can help you.

1. With extension, do you mean with the fingers and elbows?

2. Can you abduct your shoulders at a 90-degree angle?

3. Is there pain, numbness, or any sensory deficit besides motor weakness?

4. Is the atrophy patchy or seen in the whole limb? Was the onset symmetric?

5. Is there nape pain?

6. What were the results of your EMG (electromyography) and NCV (nerve conduction velocity) test?

7. Have you checked the CK-MM (creatinine kinase), ESR (erythrocyte sedimentation rate), and sugar levels?

Thank you.

Patient's Query

Hi doctor,

Thank you for the reply.

1. Most muscle groups range from the shoulders (winging scapulas), can not fully raise my arms to my fingers (the first joint of three smaller fingers). The first joint of the index fingers can move to a lesser extent. So far, not the thumbs.

2. My upper and lower arms have lost a lot of muscle mass; not sure which muscles. I can flex my elbows, but very weak at extending. Wrists also have difficulty extending and sometimes collapse while trying to carry things. Everything is symmetrical on the other side.

3. I am not diabetic. Sugar levels are typically at borderline 100 mg/dL. But years ago, when all this began, the sugar level was around 90 mg/dL.

4. EMG or NCV suggested "multifocal motor neuropathy" or "motor neuron disease" only. I have visited hospitals in my area. Do not recall having CK MM or ESR, but there was blood work at the onset, so it's possible.

5. Other symptoms worth mentioning, are intermittent patches of dry skin on shoulders, skin surface (in general) not as sensitive to heat or touch, since onset, intermittent double vision (stacked vertically) in each eye, which seems to occur from exposure to brighter lighting or electronic screens and dry eye.

With as many possible conditions out there, I have difficulty believing that it can not be narrowed down by, bilateral yet only affecting upper extremities (after 12 years or more), affecting extension functions only.

Thank you.

Hello,

Welcome back to icliniq.com.

Thank you for the additional information.

Did the weakness start on the distal or proximal part of the upper extremities? If EMG (elecromyography) states the motor neuron disease, I think you might have the flail arm variant of motor neuron disease; however, it affects extensors and flexors too. Or if it is a nerve, it is probably multifocal motor neuropathy. I cannot rule out a cervical cord lesion.

Here are my recommendations:

1. A cervical MRI (magnetic resonnce imaging) to rule oit the unusual distribution of weakness- extensor more than flexors.

2. A repeat EMG (electromyography) and NCV (nerve conduction velocity) for follow-up study if new symptoms arise (if the sensory deficit and dry patches are new onsets because motor neuron disease usually does not have sensory or autonomic deficits)

3. If the nerve is the culprit and not the motor neuron, then a trial steroid regimen might be started on you.

I am giving opinion based on your shared information. You can consult a specialist doctor for an examination of the muscles, myotomal function, sensory reflexes, and motor neuron disease flail arm variant.

Thank you.

Patient's Query

Hi doctor,

Thank you for the insight.

The first issue was the winging scapulas. Later, if I recall correctly, it started at the upper arms and worked its way toward the fingers over time. Initially, when it occurred in the upper or forearm muscles, there was a dull pain followed by muscle wasting. Not so with the scapula, wrists, or fingers. Since those initial days, I have experienced no pain, tingling, numbness, or any kind of discomfort from this. I have had cervical MRIs in the past, but no mention of lesions. There is, however, stenosis in some areas on both sides. The term used in the report is "severe stenosis," but nobody seemed to be as concerned about this as I was.

Kindly help.

Thank You.

Hello,

Welcome back to icliniq.com.

Thank you for the information.

Do you have a weakness in the facial muscles? Is there any difficulty in swallowing or speaking?

Yes, the MRI (magnetic resonance imaging) results cannot explain the symmetric painless weakness and atrophy. The EMG (electromyography) and NCV (nerve conduction velocity) of the lesions caused by the cord and nerve roots will not present with motor neuron disease results. I am thinking of scapular winging as a prominent presentation. Muscular dystrophy is another consideration that involves scapulohumeral areas. I think you must also have CK MM (creatinine kinase-skeletal muscle), which is a measure for muscle destruction- since the weakness was proximal first. And I would recommend a follow-up study of EMG and NCV. Meanwhile, while the investigation is ongoing, please undergo physical therapy to prevent rapid loss of muscle mass. I know this might be confusing, but we have to rule out all other possible causes. Finally, if it is indeed a motor neuron disease, management is supportive, and the course is progressive.

Thank you.

Same symptoms don't mean you have the same problem. Consult a doctor now!

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Dr. Florilyn Joyce Chulsi Bentrez

Neurology

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