Weakness in the Left Middle Finger: Possible Neurological Causes

Possible neurological disorders associated with weakness in the left middle finger?

Hello Doctor: My mother has myasthenia gravis and hyperthyroidism (which has been surgically removed, and she is currently taking medication to supplement potassium).
Recently, she woke up one morning with sudden weakness in her left middle finger, unable to lift it (for example, to a position like a "1").
When her left palm is facing up and she tries to make a "5," the middle finger noticeably droops.
If a pulse oximeter is clipped to the middle finger, it also droops significantly and cannot support itself, but she has no issues exerting force downward.
The other fingers on her left hand are functioning normally, and there is no numbness or pain in the entire left hand, including the middle finger.
Due to the weakness in the middle finger, movements of the entire left hand have become uncoordinated; for instance, when washing her face, she cannot press all five fingers simultaneously against her face, nor can she touch her cheek with fingers other than the middle finger first; the middle finger must bend and touch the cheek before the other fingers can follow.
Other actions that she could previously perform smoothly can still be done, but the process has become uncoordinated and awkward.
We took her to her regular follow-up appointment at the neurology department, where the doctor asked if she felt any numbness and had her test strength by pressing against his fingers.
The doctor said it did not seem like an exacerbation of myasthenia gravis and did not believe it was another neurological disease (he was concerned about ALS or Parkinson's), but he did not know why my mother was experiencing this.
I inquired about further testing with instruments, but he said it was not possible.
My mother is easily anxious and is very worried about having a rare disease, which has caused her significant anxiety.
The doctor only prescribed half a dose of an anti-anxiety medication for two weeks, suggesting that he thinks it might be a psychological issue, and advised to observe her condition after two weeks.
I would like to ask the doctor: Q1.
If there is no improvement in symptoms after two weeks, is it true that there are no tests that can clarify or rule out the cause? I have read that when there are neurological concerns, hospitals typically perform electromyography and nerve conduction studies; is it normal that we did not undergo these tests? Q2.
Could this possibly be due to potassium deficiency leading to muscle and nerve issues? Q3.
Is there a concern for hidden intracranial hemorrhage? How can we investigate this? I apologize for the lengthy message, and I appreciate your help in clarifying these concerns.
Thank you.

Guo Xiaojie, 30~39 year old female. Ask Date: 2024/05/29

Dr. Jiang Junyi reply Neurology

Dear Ms.
Kuo,
Regarding your mother's condition, we may first need to consider the common issue of trigger finger.

Q1: If there is no improvement in symptoms after two weeks, is it true that there are no tests that can identify or rule out the cause? I have read that when there are neurological concerns, hospitals often perform electromyography (EMG) and nerve conduction studies.
Is it normal that we have not done these tests?
A: If there is peripheral nerve damage, it usually presents with sensory symptoms.
Initially, the nerve conduction studies may show normal results.
Q2: Could this be due to a deficiency in potassium ions leading to muscle and nerve issues?
A: Weakness due to potassium deficiency typically affects larger muscle groups, such as difficulty rising from the toilet after use.
Q3: Is there a concern for a hidden intracranial hemorrhage? How can we investigate this?
A: Symptoms of brain hemorrhage usually affect the entire motor control area.
If the symptoms are isolated to the middle finger, the likelihood is very low.
If your mother's symptoms persist or worsen, I recommend seeking medical attention again.
For the trigger finger, you may consult a rehabilitation specialist for assistance.
Thank you for your questions.
If you have further inquiries, feel free to discuss them! Wishing you good health and peace.
Dr.
Jiang Junyi
Hua Medical/Tao Medical

Reply Date: 2024/05/29

More Info

Understanding weakness in the left middle finger, especially in the context of a family history of myasthenia gravis and thyroid issues, can be quite concerning. Your mother's sudden weakness in the left middle finger, characterized by an inability to lift it while other fingers function normally, raises several important questions regarding potential neurological causes.

Q1: Diagnostic Testing and Evaluation
If your mother's symptoms do not improve after two weeks, it is indeed reasonable to consider further diagnostic testing. While the initial examination by the neurologist may not have indicated a clear neurological disorder, it is common practice to conduct more specific tests such as electromyography (EMG) and nerve conduction studies (NCS) when there are unexplained motor deficits. These tests can help assess the electrical activity of muscles and the speed of nerve conduction, which can reveal issues such as nerve compression, neuropathy, or myopathy.

If the neurologist feels that the symptoms do not align with myasthenia gravis or other common neurological disorders, it may be beneficial to seek a second opinion or request a referral to a specialist who can perform these tests. It is important to advocate for your mother's health, especially given her anxiety about her condition.

Q2: Potassium Levels and Muscle Function
Regarding the concern about potassium levels, hypokalemia (low potassium) can indeed lead to muscle weakness and cramps. Potassium is crucial for proper muscle function, and its deficiency can result in symptoms similar to those your mother is experiencing. Since she is on medication to supplement potassium after thyroid surgery, it would be prudent to have her potassium levels checked. If her levels are low, adjusting her medication or dietary intake may help alleviate some of her symptoms.

Q3: Concerns About Intracranial Hemorrhage
The possibility of a hidden intracranial hemorrhage, such as a subdural hematoma or other types of bleeding, is a valid concern, especially if there are sudden changes in neurological function. However, these conditions typically present with additional symptoms such as severe headaches, confusion, or changes in consciousness. If your mother has not experienced any of these symptoms, the likelihood of a significant hemorrhage may be lower. Nonetheless, if there is any suspicion, imaging studies such as a CT scan or MRI of the brain can be performed to rule out any acute intracranial issues.

Conclusion
In summary, if your mother's symptoms persist, it is crucial to pursue further evaluation through appropriate diagnostic tests. Monitoring her potassium levels is also important, as deficiencies can contribute to muscle weakness. While the concern for serious conditions like myasthenia gravis or neurological disorders is understandable, it is essential to approach this systematically and with the guidance of healthcare professionals. Encourage your mother to communicate openly with her doctor about her symptoms and anxiety, as this can help in managing her condition effectively. If necessary, seeking a second opinion or additional testing can provide peace of mind and clarity regarding her health status.

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