Neurological Examination of the Upper Limbs — Viva

Short Case Viva Defence

Candidate's opening statement (model answer)

"I examined this patient's upper limbs neurologically using the systematic eight-step routine — inspection, tone, power, reflexes, coordination, sensory, cortical sensory, and functional testing. [1]

On inspection, there is wasting of the intrinsic muscles of both hands — the dorsal interossei, the thenar eminence, and the hypothenar — with visible fasciculations in the deltoid, biceps, and first dorsal interossei bilaterally. There is no tremor and no abnormal posture. [1]

Tone is increased in a spastic pattern in both arms. [1]

Power is reduced to MRC grade 4 in the finger abductors (T1), thumb opposition (T1), and shoulder abduction (C5). [1]

The reflexes are brisk at the biceps (C5/6), supinator (C5/6), and triceps (C7), with a positive Hoffman sign bilaterally. [1]

Coordination is limited by weakness — there is no intention tremor and no dysmetria in the movements the patient can perform. [1]

Sensation is entirely intact — light touch, pinprick, vibration at the distal interphalangeal joints, and joint position sense are all normal. [1]

My summary is that this patient has a combination of lower motor neuron signs (wasting, fasciculations, weakness) and upper motor neuron signs (increased spastic tone, brisk reflexes, positive Hoffman sign) with intact sensation. This is the clinical signature of motor neuron disease — amyotrophic lateral sclerosis. To complete my examination, I would examine the lower limbs for the mixed pattern, the cranial nerves for bulbar involvement (tongue wasting and fasciculations, a brisk jaw jerk), and the gait, and I would assess the respiratory function." [1]

Examiner probing questions and model answers

Q1: "Why are you confident this is motor neuron disease and not cervical spondylotic myelopathy?" [1]

"Two findings discriminate. First, the sensory exam is entirely intact — cervical myelopathy produces a sensory level or sensory loss in the upper limbs, and its absence here argues strongly against a cord compression. Second, the LMN signs are widespread across multiple levels — the deltoid (C5), the biceps (C5/6), and the first dorsal interosseus (C8/T1) — whereas cervical spondylotic myelopathy produces LMN signs confined to the myotomes at the level of the compression, with UMN signs below. The widespread fasciculations across multiple levels, combined with the intact sensation and the UMN signs in the arms themselves, are the pattern of MND, not of a single-level cord lesion. I would confirm with an MRI of the cervical spine, which in MND shows no cord compression or signal change, and with needle EMG, which shows the denervation and reinnervation across multiple spinal regions that confirms anterior horn cell disease [1][2]."

Q2: "What is the significance of the Hoffman sign, and how reliable is it?" [1]

"The Hoffman sign is the upper-limb equivalent of the Babinski sign — a pathological reflex indicating loss of cortical inhibition on the flexor reflex, consistent with a corticospinal tract lesion. It is tested by flicking the middle fingernail downward and watching for flexion and adduction of the thumb. The evidence from the systematic review by Rhee and colleagues is that the Hoffman sign has variable sensitivity (approximately 20 to 60 per cent across studies) for cervical myelopathy, and it should not be used in isolation to confirm or refute the diagnosis [3]. A bilateral or markedly asymmetric Hoffman sign is more clinically significant than a weakly positive unilateral finding, which may be present in up to 3 per cent of healthy individuals. In this patient, the Hoffman sign is positive bilaterally, and it is supported by the brisk reflexes and the increased tone, which together build the UMN picture. The teaching point is that the Hoffman sign is a screening maneuver, not a diagnostic one — the indication for an MRI is the clinical suspicion from the combination of signs, not the positivity of the Hoffman alone."

Q3: "Walk me through the eight steps of your examination and why you performed them in that order." [1]

"The order is inspection, tone, power, reflexes, coordination, sensory, cortical sensory, and functional. The order matters because each step builds on the last to localise the lesion. Inspection frames the differential — the wasted, fasciculating hands and the tremor or the posture generate the UMN-versus-LMN question before I touch the patient. Tone is the gateway — spastic tone means UMN, rigid tone means basal ganglia, hypotonic tone means LMN or cerebellum. Power by myotome localises the weakness to a root or a nerve and grades it with the MRC scale. Reflexes confirm the UMN or LMN pattern and, by their level (C5/6 biceps and supinator, C7 triceps, C8 finger jerk), localise the cord level. Coordination tests the cerebellum (finger-nose, rapid alternating movements) and screens for subtle UMN weakness (pronator drift). Sensory tests the two ascending pathways — spinothalamic (pinprick) and dorsal column (vibration, joint position) — and the distribution (dermatomal, glove, nerve territory, sensory level) localises the lesion. Cortical sensory (stereognosis, graphesthesia) tests the parietal lobe, with the caveat that primary sensation must be intact for the test to be interpretable. Functional testing reveals the impact of the deficit on daily tasks and may reveal an integration deficit missed by the segmental testing." [1]

Q4: "How would you distinguish an intention tremor from a rest tremor and from a postural tremor?" [1]

"The tremors are classified by when they occur. A rest tremor is present when the limb is fully supported and at rest, and it suppresses with voluntary movement — this is the 4-to-6 Hz pill-rolling tremor of Parkinson disease. A postural tremor is present when the limb is held against gravity (arms outstretched) and absent at rest — this is essential tremor, thyrotoxicosis, or physiological tremor. An intention tremor appears and worsens as the finger approaches the target in the finger-nose test — this is a cerebellar sign. The discriminator I use at the bedside is to observe the hands in three positions: resting in the lap (rest tremor), outstretched (postural tremor), and during the finger-nose movement (intention tremor). The Parkinsonian rest tremor is typically asymmetric, pill-rolling, and accompanied by bradykinesia and rigidity. The essential tremor is typically bilateral, improves with alcohol, and worsens with action. The cerebellar intention tremor is accompanied by dysmetria, dysdiadochokinesia, and a wide-based ataxic gait. The MDS clinical diagnostic criteria define parkinsonism as bradykinesia plus rest tremor or rigidity [4]."

Q5: "What is the significance of pronator drift, and how do you distinguish a UMN drift from a proprioceptive drift?" [1]

"Pronator drift is tested by asking the patient to hold both arms outstretched with palms supinated and eyes closed for 20 to 30 seconds. A UMN (corticospinal tract) drift is downward and pronating — the affected arm slowly sinks and the palm turns inward and downward, because the supinator muscles are weaker than the pronator muscles in a pyramidal lesion. This is often more sensitive than formal power testing for detecting subtle UMN weakness. A proprioceptive (dorsal column) drift is upward and lateral, with writhing finger movements (pseudoathetosis) — the patient cannot maintain the arm position without visual input because they have lost the joint position sense. The discriminator is the direction of the drift (downward-pronating for UMN, upward-writhing for proprioceptive) and the associated findings (brisk reflexes and increased tone for UMN, absent vibration and joint position sense for dorsal column). The key teaching point is that the eyes-closed component is what makes the test sensitive — it removes the visual compensation that can mask a subtle deficit. The candidate who tests pronator drift with the eyes open has missed the sign." [1]

Q6: "What is the single most important lesson from this case for a registrar performing the upper limb neurological examination?" [1]

"The single most important lesson is that the look test frames the differential before a single reflex is struck. The 30 seconds of inspection — looking for wasting, for fasciculations, for tremor, for posture — generated the UMN-versus-LMN question and the suspicion of MND before I touched the patient. The registrar who rushes to reflexes and misses the wasted, fasciculating first dorsal interosseus has missed the diagnosis. The corollary is the systematic routine: every step, in the same order, every time, with the interpretation building toward the localisation. The candidate who skips the sensory exam, or who tests coordination in a weak limb and calls it dysmetria, or who grades all power as 4 without specifying the pattern, has lost the information that the localisation requires. The upper limb neurological examination is not a checklist — it is a structured argument, and the candidate who presents it as such has demonstrated the core neurological competency the examiner is testing." [1]