What is the standard scale for deep tendon reflex (DTR) grading?

Deep Tendon Reflex Grading Scale

The standard scale for deep tendon reflex (DTR) grading is the NINDS (National Institute of Neurological Disorders and Stroke) Myotatic Reflex Scale, which has demonstrated substantial to near-perfect reliability and is recommended as a universal scale for clinical use. 1

Standard NINDS Myotatic Reflex Scale

The universally accepted grading system uses a 5-point scale:

• 0 = Absent reflex - No response detected even with reinforcement 1
• 1+ = Hyporeflexia/Diminished - Reflex present but decreased, low normal 1
• 2+ = Normal - Average, expected response 1
• 3+ = Brisker than average - May indicate disease but can be normal in anxious patients 1
• 4+ = Hyperreflexia - Very brisk, often with clonus, indicative of upper motor neuron pathology 1

Clinical Reliability and Validation

• The NINDS scale demonstrates substantial to near-perfect intraobserver reliability and moderate-to-substantial interobserver reliability across different examiners 1
• Reflexes in the lower extremities show better reproducibility than those in the upper extremities 1
• Neither educational background nor additional training sessions significantly influenced the reliability of the scale, indicating its robustness across different clinical settings 1

Quantitative Features Supporting Grading

While the NINDS scale remains the clinical standard, understanding the underlying biomechanics improves accuracy:

• Peak tap force ranges used by clinicians: 0-20 Newtons for hyperreflexia, 21-50 Newtons for normoreflexia, and >50 Newtons for hyporeflexia 2
• Briskness (knee excursion divided by peak tendon tap force) is the best distinguishing feature between hyper- and normoreflexic responses 2
• Angular velocity is the most stable and reproducible kinesiological parameter for reflex assessment 3

Clinical Context and Interpretation

• Hyperreflexia (3+ to 4+) with increased tone and abnormal plantar reflex (Babinski sign) indicates upper motor neuron pathology 4
• Hyporeflexia or areflexia (0 to 1+) with associated weakness and decreased muscle bulk suggests lower motor neuron or muscle disorders 4
• Asymmetry between sides is often more clinically significant than the absolute grade 4

Common Pitfalls to Avoid

• Do not rely solely on reflex grading without considering associated findings such as tone, strength, and plantar responses 4
• Avoid using inadequate hammer force, which can falsely suggest hyporeflexia - ensure consistent technique with appropriate force application 2
• The Taylor hammer has a ceiling effect in the hyporeflexic range due to its small mass and short handle; consider using a Babinski or Queen Square hammer for suspected hyporeflexia 2
• Patient anxiety or muscle tension can artificially elevate reflex responses; use reinforcement maneuvers (Jendrassik maneuver) when reflexes appear diminished 5