The Wartenberg Wheel: A Comprehensive Guide to Dermatomal Innervation Testing

Introduction

The Wartenberg wheel is a diagnostic tool used by neurologists to assess the level of sensory innervation, or the integrity of the nerves that carry sensory information from the skin to the spinal cord and brain. Developed by Dr. Robert Wartenberg in the early 20th century, this simple yet effective device has become a staple in neurological examinations.

How Does the Wartenberg Wheel Work?

The Wartenberg wheel consists of a rotating disc with 12 radiating spokes, each of which corresponds to a specific dermatome. Dermatomes are areas of skin supplied by a single spinal nerve root. By applying pressure to each spoke in turn, the examiner can determine which dermatomes are intact and which may be affected by nerve damage.

Clinical Significance

The Wartenberg wheel is a valuable tool for diagnosing a wide range of neurological conditions, including:

• Peripheral nerve injuries
• Radiculopathies (nerve root compression)
• Spinal cord injuries
• Multiple sclerosis
• Guillain-Barré syndrome

By identifying the affected dermatomes, the examiner can pinpoint the location of the nerve damage and determine the severity of the condition. This information is crucial for planning appropriate treatment and monitoring patient recovery.

Wartenberg Wheel Test Procedure

The Wartenberg wheel test is a relatively simple and painless procedure. The patient is seated or lying down with their arm or leg exposed. The examiner applies firm but gentle pressure to each spoke of the wheel, starting from the most distal (furthest from the body) and working proximally (towards the body). The patient is asked to report any sensations they feel, such as pain, numbness, or tingling.

Note: The Wartenberg wheel should not be used on areas of skin with open wounds or infections.

Results Interpretation

A normal Wartenberg wheel test result indicates that all dermatomes are intact and receiving sensory innervation. Abnormal results may include:

• Hypoesthesia (decreased sensation) or anesthesia (complete loss of sensation) in one or more dermatomes, suggesting nerve damage in that area
• Hyperesthesia (increased sensitivity) in one or more dermatomes, indicating irritation or inflammation of the affected nerve
• Paresthesia (abnormal sensations, such as tingling or burning) in one or more dermatomes, suggesting nerve damage or irritation

Wartenberg Wheel Tables

Table 1: Dermatomal Innervation of the Upper Extremities

Table 2: Dermatomal Innervation of the Lower Extremities

Table 3: Dermatomal Innervation of the Head and Neck

Stories and Lessons Learned

Story 1:

A 25-year-old male presented with numbness and tingling in his right hand. A Wartenberg wheel test revealed decreased sensation in the C6 and C7 dermatomes, suggesting nerve damage in the radial and median nerves, respectively. An MRI scan confirmed a herniated disc at the C5-C6 level, which was compressing the affected nerves.

Lesson: The Wartenberg wheel can help localize the site of nerve damage, guiding further diagnostic testing and treatment.

Story 2:

A 70-year-old female with diabetes mellitus complained of pain and weakness in her left leg. A Wartenberg wheel test revealed hyperesthesia in the L5 and S1 dermatomes, indicating irritation or inflammation of the sciatic nerve. Electromyography (EMG) confirmed a diagnosis of diabetic neuropathy, a condition that damages peripheral nerves due to high blood sugar levels.

Lesson: The Wartenberg wheel can help differentiate between different types of nerve damage, such as compression and inflammation.

Story 3:

A 32-year-old female suffered a traumatic brain injury in a car accident. A Wartenberg wheel test showed complete loss of sensation in the entire left side of her body, indicating damage to the left spinothalamic tract in the spinal cord.

Lesson: The Wartenberg wheel can detect sensory deficits caused by spinal cord injuries, providing valuable information for prognosis and rehabilitation planning.

Tips and Tricks

• Use a light touch when applying pressure to the spokes to avoid causing discomfort to the patient.
• Ask the patient to close their eyes during the test to minimize visual cues.
• Test both sides of the body for comparison, even if the patient only reports symptoms on one side.
• If the patient has difficulty identifying the sensations they feel, use a cotton swab or a sharp object to stimulate the skin lightly.

Common Mistakes to Avoid

• Incorrect positioning: Ensure that the patient is in a comfortable position and that the limb being tested is properly supported.
• Inconsistent pressure: Apply firm but gentle pressure to each spoke consistently to ensure accurate results.
• Overreliance on the test: The Wartenberg wheel is a valuable tool, but it should not be used as the sole diagnostic method. Always consider the patient's history, physical examination findings, and other diagnostic tests.
• Ignoring subtle findings: Even slight changes in sensation may indicate nerve damage. Do not dismiss any abnormal findings, regardless of how minor they may seem.

Pros and Cons of the Wartenberg Wheel

Pros:

• Simple, inexpensive, and easy to use
• Can be performed at the bedside
• Provides quick and reliable information about sensory innervation
• Useful for screening and localizing nerve damage

Cons:

• Requires some experience and skill to interpret
• May be difficult to perform on patients with altered mental status or cognitive impairment
• Does not provide detailed information about the severity or type of nerve damage

Conclusion

The Wartenberg wheel is a versatile and cost-effective tool that neurologists rely on to assess sensory innervation and diagnose a wide range of neurological conditions. By interpreting the results of the Wartenberg wheel test in conjunction with other clinical findings, practitioners can accurately pinpoint the location and extent of nerve damage and develop appropriate treatment plans.