Focal Neurological Signs: Key Indicators of Neurological Disorders
Focal neurologic signs are essential in determining what’s going wrong in the brain. They are a collection of symptoms that allow a practitioner to identify what is happening quickly and accurately. Moreover, because they are typically more severe in nature, they often point to severe issues that require immediate medical attention. This article will cover what focal neurologic signs are, what they mean, and who you should see if they present themselves. While this is not medical advice, this information is designed to give you a good enough understanding of what is life-threatening and when you should seek immediate medical care.
What Are Focal Neurological Signs?
Focal neurologic signs are localized symptoms that indicate dysfunction in a specific location. While general symptoms tend to affect multiple systems and a broad area, focal symptoms affect smaller, more specific areas. This specificity enables a trained neurologist to identify pathology more easily and recommend the appropriate testing and treatment.
Common Symptoms
Focal neurological signs can vary in presentation and severity. They indicate something wrong with the nerves, spinal cord, brain structures, or deeper brain structures. Some common symptoms include weakness, paralysis, aphasia, visual field loss, ataxia, focal seizures, and sensory loss. Others not covered in this article include hemiparesis, hemiplegia, dysarthria, anosmia, dysphagia, facial palsy, double vision, alexia, and agraphia. The silver lining with focal neurologic symptoms is they are often easy to localize due to their predictable presentation. The sooner you can identify the symptoms and get help, the better. A summary of the first 6 symptoms is provided below.
1. Weakness or Paralysis
The inability to use muscle points to a potential issue in the somatosensory strip, spinal cord, or nerve plexus. Injuries, TIAs, strokes, concussions, viruses, and hemiplegic migraines are common causes of weakness or paralysis. If the onset is abrupt and seemingly out of nowhere, call emergency care immediately. The most common reason for spontaneous weakness on one side is a stroke-related event, which requires immediate medical attention.
2. Aphasia
Aphasia is the difficulty expressing or understanding language. There are multiple types of aphasia, but the two most common are difficulty speaking and understanding words. Broca’s aphasia occurs in the left frontal lobe. It manifests as an inability to speak words even if you understand them. Wernicke’s aphasia is localized to the temporal lobe and presents an inability to understand spoken language. Familiar sources of aphasia involve TIA, concussions, tumors, viruses, neuro-degenerative conditions, and encephalitis. If you suspect it’s occurring from a stroke due to rapid onset and no prior issues, call emergency medical care immediately.
3. Visual Field Loss
A sudden loss of one visual field is called a hemianopia. Someone experiencing this will lose half of the visual field in one or both eyes, depending on the localization of the issue. Causes include trauma, infection, neurodegenerative conditions, tumors, vascular changes or damage, migraine, or seizures. The exact localization requires a trained professional and a detailed understanding of where and how much of the visual field is impacted.
4. Ataxia
Ataxia occurs when there is damage to an area of the brain called the cerebellum. The cerebellum involves planning and executing planned motor movements, such as walking or picking something up with your hands. Causes include brain damage, neurodegenerative disorders, cerebral palsy, infection, MS, and hereditary genetic disorders. Treatment varies widely based on the source of the ataxia.
5. Focal Seizures
When seizures originate from and affect only one part of the body, it typically indicates disturbances in specific brain regions. These seizures can be localized based on which area is affected by the seizure. However, the exact course of action varies based on the underlying cause. Causes for focal seizures include brain injury, genetic conditions, infection, substance withdrawal, and vascular events. Treatment can range from medication to surgery to physical rehab.
6. Sensory Loss
Reduction or loss of sensation in a specific area of the body correlates with damage to the sensory pathways of the brain or spinal cord. It can also point to an issue with the brain area that receives input from the body, called the somatosensory strip. There are a variety of conditions that include sensory loss as a primary symptom, so you should be sure to obtain a thorough physical and neurologic workup to ensure it is not part of a more significant problem. Causes of sensory loss include injury, genetic disorders, illness, neuropathy, medications, and vascular events.
Causes of Focal Neurologic Signs
Recognizing focal neurological signs is essential for healthcare providers as they offer clues about the area of the nervous system that may be impaired. These signs help in:
Focal neurological symptoms occur when specific parts of the brain, spinal cord, or peripheral nerves are damaged or malfunctioning. Various conditions can cause these localized symptoms, each affecting the nervous system differently. Below is a list of common causes of focal neurological symptoms:
1. Stroke (Ischemic or Hemorrhagic): Sudden loss of blood flow leading to tissue death and subsequent loss of function of local tissue.
2. Transient Ischemic Attack (TIA): People will often refer to this as a mini-stroke as it mimics some of the symptoms without extensive damage. A TIA is characterized by a short disruption in blood flow, which temporarily affects function in that area of the brain.
3. Brain Tumor: Benign and malignant tumors can grow and compress nearby tissue. When the tumor compresses the tissue, it loses blood flow and thus function.
4. Traumatic Brain Injury (TBI): Depending on the severity and mechanism of the injury, a TBI can affect structures local to the injury, on the opposite side of the injury, or deep within the brain stem. These symptoms may appear immediately after the trauma or weeks to months later.
5. Infections: Certain infections can affect specific brain areas, leading to focal symptoms. These include meningitis, neurosyphilis, encephalitis, and abscesses.
6. Multiple Sclerosis (MS): MS is a demyelinating condition, which means the fatty coating that wraps nerves begins to unwind. Depending on the localization and severity of the condition, symptoms will vary and generally progress slowly until it is treated and managed by a specialist.
7. Brain Hemorrhage: Bleeding within or around brain tissue can disrupt normal brain function in specific areas.
8. Epilepsy: Seizure disorders originating from specific brain focal points can present localized symptoms during an episode.
9. Neurodegenerative Diseases: Alzheimer’s, Parkinson’s, and Huntington’s disease are all examples of neurodegenerative diseases. They often cause focal symptoms as they progress.
10. Cerebral Aneurysms: These occur when a blood vessel bulges or expands. This expansion presses on nearby tissue and causes symptoms based on the location and size.
11. Arteriovenous Malformation (AVM): An abnormal connection between arteries and veins in the brain can disrupt blood flow and oxygen delivery, causing localized neurological symptoms.
12. Spinal Cord Injury: Damage or disease in and around the spinal cord will produce motor and sensory issues at the level of the lesion and often below it.
13. Peripheral Neuropathy: Damage to peripheral nerves, inflammatory disease, or diabetes can dampen the signals from peripheral nerves, resulting in sensory issues, numbness, and tingles.
14. Cervical Spondylosis: Degenerative changes in the cervical vertebrae can put pressure on the nerve root, affecting the output and sensory input at the affected level. This will typically follow a predictable dermatomal pattern.
15. Brain Abscess: A collection of pus caused by an infection in the brain can affect specific brain functions depending on its location.
16. Subdural Hematoma: Blood accumulating beneath the outer covering of the brain (dura) after trauma can cause focal neurological deficits, depending on the hematoma’s location.
Conclusion
Focal neurologic signs can provide a great deal of insight into what’s happening and where it’s happening. Keep a close eye on even mild signs before they progress to pathology, as early detection is crucial for preventing more serious issues. Follow the mantra “better safe than sorry” if you suspect you’re experiencing mild focal problems.
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*Note: The information provided in this article is for educational purposes only and does not constitute a doctor-patient relationship. Patients should consult their medical provider or primary care physician before trying any remedies or therapies at home.
