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Wrist Drop Test

Exams and Signs

Historical Overview

  • Wrist drop—which may also be referred to as radial nerve palsy—can develop through a variety of central or peripheral causes and impairs the patient’s ability to extend the wrist.1,2
  • When damage to the radial nerve is suspected, electrodiagnostic and radiological studies are helpful for identifying the exact injury location and degree of damage; however, a physical examination that includes the wrist drop test should be performed first to determine if additional tests are needed.3,4

Description

  • The wrist drop test is a simple examination of the wrist that is primarily used to identify wrist drop, but can also detect the presence of lateral epicondylitis, wrist extensor weakness, or atrophy of the area from a long-standing radial nerve lesion.

Pathophysiology

  • Wrist drop is caused by damage to the radial nerve, which travels down the arm and controls the movement of the triceps muscle at the back of the upper arm. Patients with wrist drop are unable to abduct the thumb or extend the wrist against moderate resistance, and finger flexion is also impaired.2,5
  • There are a variety of potential causes of radial nerve palsy that leads to wrist drop, which can occur through either central or peripheral mechanisms. Some of the most common causes include lacerations, humerus fractures, lead poisoning, alcoholism, stroke, and radial nerve entrapment.1,2,5
  • The most frequent cause of isolated peripheral wrist drop is compression neuropathy, which may result from unintended prolonged pressure on the radial nerve after sleeping on the arm in an intoxicated state. Its clinical symptoms include motor weakness with sensory disturbances and are similar to stroke or a herniated cervical disc and other neuropathies.1,2

Instructions

  1. Obtain an accurate and complete patient history with a description of the injury if applicable.
  2. Have the patient sit down and assume the “praying position” with the hands and palms placed together in dorsiflexion.
  3. Ask the patient to pull the palms apart ~0.5 in. and hold them in this position for up to 1 minute.
  4. Observe the position of the wrist in question during this time.

Related Signs and Tests

  • MRI
  • High-resolution ultrasound
  • Nerve conduction studies
  • Alternative clinical examination: ask the patient to grasp the clinician’s hand firmly. In this movement, there is normally simultaneous contraction of the long extensor and flexor muscles of the forearm, in order to keep the wrist fixed in the stretched position, which is required to permit a strong flexion of the fingers.3
  • A differential diagnosis of acute stroke should be kept in mind to rule out causes for isolated hand weakness.1

Diagnostic Performance Characteristics

  • If it has been determined that source of the wrist drop is from a peripheral origin, the next step is to deduce if the patient has an isolated radial nerve lesion or if the radial nerve palsy is part of a polyneuropathy.
  • Except in cases of unambiguous situations like wrist drop following humerus fracture or surgery, it is advised to examine the functions of the other peripheral nerves of the four limbs. The reason is that a radial nerve lesion is not infrequently promoted by a preexisting polyneuropathy, which may have been “silent” up to the occurrence of wrist drop.

Additional Information

Presentation Photos and Related Diagrams
Wrist Drop
  • Right partial wrist drop in patient with a Saturday night's palsy.
    Right partial wrist drop in patient with a Saturday night's palsy.
Definition of Positive Result
  • A positive result occurs when the patient is unable to maintain wrist dorsiflexion.
Definition of Negative Result
  • A negative result occurs when the patient is able to maintain wrist dorsiflexion.
Comments and Pearls
  • Diagnosing isolated wrist drop as an acute motor area stroke is very difficult, but high-risk factors like old age, diabetes, and hypertension should help to confirm the diagnosis if nerve conduction studies are normal.1
Diagnoses Associated with Exams and Signs
References
  1. Goel, K, Singh, SK, Agarwal, H, et al. Isolated Wrist Drop Presenting as Acute Stroke: Rare Case Report with Review of Literature. J Neurosci Rural Pract 2018;9(4):647-649.PMID: 30271070
  2. Dsouza, HS, Dsouza, SA, Menezes, G, et al. Evaluation and treatment of wrist drop in a patient due to lead poisoning: case report. Ind Health 2009;47(6):677-80. PMID: 19996545
  3. Poeck, K. Wrist Drop in: Diagnostic Decisions in Neurology, Heidelberg (ed), Berlin, Springer-Verlag, 1985 pp. 158-159. 
  4. Bumbasirevic, M, Palibrk, T, Lesic, A, et al. Radial nerve palsy. EFORT Open Rev 2016;1(8):286-294. PMID: 28461960
  5. Han, BR, Cho, YJ, Yang, JS, et al. Clinical features of wrist drop caused by compressive radial neuropathy and its anatomical considerations. J Korean Neurosurg Soc 2014;55(3):148-51. PMID: 24851150
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