From the Guidelines
Loss of tendon reflexes is primarily caused by damage to the reflex arc pathway, which can occur at various points in the nervous system, with the most common causes including peripheral neuropathies, spinal cord disorders, and certain medications, as well as metabolic disorders and aging. The reflex arc pathway involves the afferent nerve, spinal cord, and efferent nerve, and damage to any of these components can lead to loss of tendon reflexes. Peripheral neuropathies, such as diabetic neuropathy, Guillain-Barré syndrome, and chronic inflammatory demyelinating polyneuropathy, can damage the sensory or motor nerves involved in reflexes, leading to decreased or absent reflexes 1. Spinal cord disorders, including spinal cord injury, vitamin B12 deficiency, and tabes dorsalis, can interrupt the reflex pathway at the spinal level, resulting in loss of tendon reflexes 1. Certain medications, such as phenytoin, carbamazepine, and some chemotherapy drugs, can also affect nerve function and diminish reflexes. Metabolic disorders, including hypothyroidism and uremia, can affect nerve function and reflexes, and aging naturally leads to some reflex reduction.
Some of the key causes of loss of tendon reflexes include:
- Peripheral neuropathies, such as diabetic neuropathy, Guillain-Barré syndrome, and chronic inflammatory demyelinating polyneuropathy
- Spinal cord disorders, including spinal cord injury, vitamin B12 deficiency, and tabes dorsalis
- Certain medications, such as phenytoin, carbamazepine, and some chemotherapy drugs
- Metabolic disorders, including hypothyroidism and uremia
- Aging, which naturally leads to some reflex reduction
- Acute conditions, such as spinal shock following trauma, which can cause temporary reflex loss
In evaluating absent reflexes, doctors typically consider the pattern of loss, associated symptoms, and medical history to determine the underlying cause, as this helps guide appropriate treatment for the specific condition affecting the nervous system 1. It is essential to note that the loss of tendon reflexes can have significant implications for morbidity, mortality, and quality of life, and prompt diagnosis and treatment are crucial to prevent long-term damage and improve outcomes.
From the Research
Causes of Loss of Tendon Reflexes
The loss of tendon reflexes can be attributed to various factors, primarily related to damage or conditions affecting the peripheral nervous system. Some of the key causes include:
- Peripheral neuropathies, which are a group of conditions caused by damage to the peripheral nervous system 2
- Metabolic disorders, such as diabetes, which can lead to peripheral neuropathy and subsequently affect tendon reflexes 2, 3
- Drug-related and systemic etiologies, which can also contribute to the development of peripheral neuropathy 2
- Nerve compression or injury, which can directly impact the function of nerves responsible for tendon reflexes 3
- Alcohol use, toxin exposure, hereditary diseases, and nutritional deficiencies, all of which are identifiable causes of peripheral neuropathy 3
- Idiopathic cases, where the cause of peripheral neuropathy and subsequent loss of tendon reflexes cannot be identified, accounting for 25% to 46% of cases 3
Underlying Mechanisms
The underlying mechanisms often involve damage to the axons or myelin sheath of the nerves, leading to impaired nerve function and reduced or lost tendon reflexes. Management of the underlying cause, such as controlling blood glucose levels in diabetic patients or correcting vitamin deficiencies, can help in restoring nerve function and potentially improving tendon reflexes 2, 3