The Hoffman sign is a clinical neurological test to assess the nervous system. It is a simple physical examination maneuver to evaluate reflexes in the upper extremities. This article clarifies what a positive result signifies.
Understanding the Hoffman Sign
The Hoffman sign, also known as the digital reflex or snapping reflex, is elicited through a physical maneuver. A clinician holds the patient’s middle finger at the joint closest to the fingernail and then flicks the nail downward. A positive sign occurs when this flicking motion causes involuntary flexion or twitching of the patient’s thumb and index finger. This response is hyperreflexia, indicating nervous system overreaction.
The test is a quick, equipment-free method to assess for upper motor neuron dysfunction. Upper motor neurons originate in the brain and travel down the spinal cord, controlling voluntary movement and muscle tone. An abnormality in these pathways, often due to brain or spinal cord issues, can lead to an exaggerated reflex response.
Interpreting a Positive Result
A positive Hoffman sign suggests the presence of an upper motor neuron lesion, which refers to damage or disruption within the corticospinal tract, a primary motor control pathway. This sign is commonly associated with cervical myelopathy, a condition involving spinal cord compression in the neck. Such compression can result from degenerative changes like disc degeneration, spinal stenosis, or ligament ossification, leading to impaired communication between the brain and spinal cord.
The hyperreflexia observed in a positive Hoffman sign occurs because the normal inhibitory signals from the brain that temper spinal reflexes are disrupted. This disruption allows the reflex arc in the spinal cord to produce an exaggerated response. While cervical myelopathy is a significant concern, a positive Hoffman sign can also be seen in other neurological conditions such as multiple sclerosis, vitamin B12 deficiency, or systemic disorders like hyperthyroidism and anxiety.
A positive Hoffman sign, particularly if it occurs only on one side of the body, can indicate a nervous system injury. The sign is more prevalent in severe myelopathy, but can also appear with less severe neurological deficits. While the test can aid in diagnosis, it is not considered a standalone diagnostic tool for spinal cord compression.
Nuance and Further Evaluation
A positive Hoffman sign is a clinical finding and not a definitive diagnosis on its own. Approximately 3% of healthy individuals may exhibit a positive Hoffman sign without any underlying neurological problems or spinal cord compression. This phenomenon is sometimes referred to as a physiological Hoffman’s reflex.
A positive finding must be correlated with a patient’s other clinical symptoms, medical history, and additional neurological examination findings. If a positive Hoffman sign is present, especially if it is markedly active or asymmetrical, further evaluation is warranted. This often includes imaging studies, such as a magnetic resonance imaging (MRI) scan of the cervical spine, to assess for spinal cord compression or other structural abnormalities.
MRI is considered the primary diagnostic tool for cervical myelopathy and can reveal changes in the spinal cord. Consultation with specialists, such as neurologists or neurosurgeons, is a common next step to interpret findings within the broader clinical picture and determine the appropriate course of action.