Ramsay Hunt syndrome type 3

Ramsay Hunt syndrome type 3, also called Hunt's disease or artisan's palsy, is an occupationally associated neuropathy of the deep palmar branch of the ulnar nerve in which compression within or just distal to the ulnar tunnel produces weakness and wasting of the intrinsic muscles of the hand

The syndrome is entirely unrelated to the much better known Ramsay Hunt syndrome type 1, which is herpes zoster of the geniculate ganglion with facial palsy, and to type 2, a progressive myoclonic epilepsy, and the three share only the name of the neurologist who described them

Because the deep branch is purely motor, the typical patient has progressive weakness and wasting without the sensory loss that characterises most other ulnar neuropathies, which is why the condition is easily mistaken for a tendon injury or a motor neuron disease

Terminology and classification

• The preferred anatomical label is neuropathy or compression of the deep palmar branch of the ulnar nerve, and Ramsay Hunt syndrome type 3 is retained mainly as an eponym in historical and reference literature
• Hunt's disease and artisan's palsy are synonyms, and the latter reflects the historical observation that the disorder clustered among craftsmen whose work required repeated pressure or gripping with the base of the palm
• It is classified as a focal mononeuropathy and specifically as a distal ulnar tunnel syndrome, in contrast to proximal ulnar neuropathy at the elbow, which is far more common and produces a different pattern of sensory and motor loss
• Within the ulnar tunnel, compression can occur in the proximal segment before the bifurcation, the distal motor segment after the bifurcation, or the superficial sensory segment, and only the motor-predominant distal pattern corresponds to classic Ramsay Hunt syndrome type 3
• ICD-10 codes the lesion under G56.2 for lesion of the ulnar nerve, and no dedicated ICD-11 code exists for the eponym, so coding depends on the broader ulnar neuropathy category
• The main named differentials are cubital tunnel syndrome, carpal tunnel syndrome, C8 or T1 radiculopathy, motor neuron disease, syringomyelia and thoracic outlet syndrome, each separated by the distribution of sensory loss, reflex changes and electrodiagnostic findings

History

• James Ramsay Hunt, an American neurologist who lived from 1872 to 1937, described a form of progressive wasting of the hand muscles in artisans and attributed it to injury of the deep palmar branch of the ulnar nerve
• Hunt's broader work on the ulnar nerve also produced the eponym Hunt's disease, and he described herpes zoster oticus in 1907 and myoclonic epilepsy in 1921, so the later numbering of Ramsay Hunt syndromes as types 1, 2 and 3 was a retrospective convention rather than a classification he proposed
• A 1960 clinical and electrical study by Ebeling, Gilliatt and Thomas characterised ulnar nerve lesions in the hand, and the 1969 classification of Shea and McClain divided ulnar tunnel syndrome into three patterns and helped separate distal palmar compression from lesions at the elbow
• Hankey and Gubbay reported in 1988 two cyclists with mononeuropathy of the deep palmar branch caused by prolonged pressure from bicycle handlebars, and one recovered rapidly after modifying the hand grip
• High-resolution ultrasound and magnetic resonance imaging in the 1990s and 2000s allowed direct visualisation of ganglion cysts, ulnar artery abnormalities and hook of hamate fractures that had previously been found only at surgery
• Modern series of hook of hamate fractures in racket and bat athletes, and of handlebar palsy in endurance cyclists, have refined the clinical recognition of the disorder and shifted emphasis toward early imaging and cause-specific surgery

Epidemiology

• Ramsay Hunt syndrome type 3 is rare and no population-based prevalence has been published, so incidence estimates are derived from case series such as the 1988 report by Hankey and Gubbay and from surveys of occupational and sporting groups
• Historical series concentrated among artisans such as carpenters, blacksmiths, shoemakers and metalworkers whose palms were repeatedly compressed by tools or workpieces
• Cycling is the most frequently reported modern cause, and handlebar palsy occurs in endurance riders, mountain bikers and riders who rest the hypothenar eminence on the bar for long periods
• Other reported groups include motorcyclists, wheelchair users, users of vibrating hand tools, racket and bat athletes, and workers who lean on the ulnar side of the palm at a bench
• Most occupational series show a male predominance, probably reflecting the sex distribution of the relevant jobs rather than a biological susceptibility of the nerve
• The condition is usually unilateral and affects the dominant hand, although bilateral cases occur in cyclists and in workers who use both hands symmetrically
• It is probably underdiagnosed because pure motor weakness without numbness is attributed to overuse, arthritis or tendon problems, and because mild cases recover after rest without medical attention
• Ulnar tunnel syndrome as a whole is much less common than carpal tunnel syndrome, which accounts for about 90% of entrapment neuropathies, and the deep palmar branch variant is the least common of the ulnar tunnel patterns

Pathophysiology

• The ulnar nerve enters the hand through the ulnar tunnel, or Guyon canal, whose boundaries include the pisiform, the hook of the hamate, the pisohamate ligament and the hypothenar muscles
• Within the tunnel the nerve divides into a superficial sensory branch supplying the little finger and the ulnar side of the ring finger, and a deep motor branch that curves around the hook of the hamate to supply most intrinsic muscles
• The deep branch supplies the hypothenar muscles, the palmar and dorsal interossei, the third and fourth lumbricals, the adductor pollicis and the deep head of flexor pollicis brevis, which explains the pattern of wasting and weakness
• Compression first produces focal demyelination with conduction block, and sustained pressure causes axonal loss with denervation of the intrinsic muscles and fatty replacement if reinnervation does not occur
• Ganglion cysts arising from the pisotriquetral joint are the commonest mass lesion, followed by hook of hamate fracture, pisiform fracture, ulnar artery aneurysm or thrombosis and anomalous hypothenar muscles
• Repetitive external pressure, as in cycling or craft work, produces a compressive neuropathy without a mass, and this mechanism explains the historical association with artisans and the modern association with handlebars

Clinical features

• Patients report progressive weakness of grip and pinch, difficulty separating the fingers, dropping objects and clumsiness of the hand, while sensation in the fingers is usually preserved
• Wasting is visible in the hypothenar eminence and in the first dorsal interosseous muscle, producing a hollow between the thumb and index finger and a flattened ulnar border of the hand
• Froment's sign is positive when thumb flexion compensates for weak adductor pollicis during pinch, and Wartenberg's sign reflects weak third palmar interosseous with an abducted little finger
• Ulnar clawing of the ring and little fingers may appear in chronic cases, and the clawing is less marked than in proximal ulnar lesions because the long flexors remain intact
• Tenderness may be elicited over the hook of the hamate or the ulnar tunnel, and a Tinel sign can sometimes be produced by tapping over the tunnel, although these signs are inconsistent
• A history of cycling, craft work, vibration exposure or a Fall on the outstretched hand should be sought, because it points to the mechanism and determines whether imaging for fracture or mass is required

Diagnosis

• The diagnosis is suspected from the combination of pure motor ulnar intrinsic weakness, a compatible occupational or sporting history and tenderness over the ulnar tunnel, with sensory examination serving mainly to exclude other lesions
• Nerve conduction studies show prolonged distal motor latency to the intrinsic muscles or reduced compound muscle action potential amplitude, while sensory conduction in the superficial branch is normal in pure deep-branch lesions
• Needle electromyography confirms active denervation and chronic reinnervation in the hypothenar and interosseous muscles and helps distinguish the lesion from a C8 or T1 radiculopathy or a generalised motor neuron disease
• Ultrasound is the first-line imaging method and can measure nerve cross-sectional area, detect a ganglion cyst and assess the ulnar artery, while magnetic resonance imaging is used when a mass or marrow lesion is suspected
• Plain radiographs and computed tomography are indicated after trauma or in athletes with ulnar-sided wrist pain, because hook of hamate and pisiform fractures are easily missed on standard views
• The differential includes cubital tunnel syndrome, carpal tunnel syndrome, C8 or T1 radiculopathy, syringomyelia, amyotrophic lateral sclerosis, thoracic outlet syndrome and tendon rupture of the intrinsic muscles

Management

• Conservative management is first-line for compression without a mass and includes rest from the provoking activity, padding or repositioning of handlebars and tools, wrist splinting in a neutral position and non-steroidal anti-inflammatory drugs
• Cyclists should be assessed for handlebar width, reach, saddle position and grip, because small changes in bike fit can relieve hypothenar pressure and allow continued training
• Occupational therapy addresses tool design, work posture, vibration damping and scheduled breaks, and nerve gliding exercises may be used once acute compression has settled
• Ganglion cysts, ulnar artery aneurysms and symptomatic hook of hamate fractures are treated surgically, because decompression alone will not relieve compression caused by a mass or an unstable fracture
• Surgical decompression or neurolysis of the deep branch is offered when weakness is progressive, when a mass is present or when conservative treatment fails after an adequate trial
• Corticosteroid injection into the ulnar tunnel is not established and carries a risk of intraneural injection and nerve injury, so it should not replace cause-directed treatment or surgery
• Postoperative rehabilitation includes early protected motion, oedema control and progressive strengthening, with return to cycling or craft work guided by pain, wound healing and recovery of grip rather than by a fixed timetable
• Prognosis is good when compression is relieved before severe atrophy, but chronic denervation with fatty replacement of the intrinsic muscles limits recovery, so early recognition and removal of the cause are the main determinants of outcome

Research and controversies

• The evidence base consists mainly of case series and small retrospective cohorts, and no randomised trial has compared conservative treatment with early surgery for deep palmar branch compression
• The optimal timing of surgery is uncertain, because some patients recover with activity modification alone while others present with irreversible atrophy after months of unrecognised compression
• Whether high-resolution ultrasound should be used to screen high-risk workers and endurance cyclists is debated, because asymptomatic nerve enlargement and incidental ganglia are common and may lead to unnecessary intervention
• The distinction between Ramsay Hunt syndrome type 3 and other distal ulnar tunnel patterns is inconsistently applied in the literature, which complicates comparison of surgical outcomes across series
• Return-to-sport protocols after decompression or fracture fixation are based on expert opinion rather than controlled data, and prospective studies with grip strength, nerve conduction and patient-reported outcomes are needed