Chapter 56 Entrapment Neuropathies Flashcards
KEY POINTS 1. When an entrapment neuropathy is clinically suspected, electrodiagnostic testing should be performed to confirm the diagnosis and exclude other neurologic diseases including "double crushes." 2. Pressure in the carpal tunnel increases with flexion and extension of the wrist, often provoking symptoms. 3. The ulnar nerve is most vulnerable to impingement at the humeroulnar aponeurotic arcade, also called the cubital tunnel, or just a few centimeters proximally across the ulnar g
Provocative maneuvers
briefly increase pressure
at a site of compression, aid diagnosis by re-creating or
exacerbating symptoms.
When an entrapment neuropathy is clinically suspected
electrodiagnostic testing should be performed to confirm
the diagnosis and exclude other neurologic disorders
If
electrodiagnostic testing suggests that the site of compression
or entrapment is not typical
then magnetic resonance imaging or ultrasonagraphy
should be performed to identify the source of compression
“double crush”
an individual to have two
neuropathic lesions in the same limb involving the same nerves at different sites
Electrodiagnostic testing
provide prognostic
information. Electrodiagnostic testing can often differentiate
myelin dysfunction from axon damage.
neurapraxic
injury when a compressive lesion causes only focal demyelination
Site of Entrapment
of Brachial plexus
Anterior and medial scalene muscle
Subclavius muscle
Pectoralis minor and coracoid process
Cervical rib or band, medial antebrachial cutaneous nerve
Site of Entrapment
of Suprascapular
Transverse scapular ligament, scapular notch or foramen
Spinoglenoid ligament or notch
Site of Entrapment
of Musculocutaneous
Coracobrachialis muscle
Brachial fascia, lateral antebrachial cutaneous nerve
Site of Entrapment
of Axillary
Quadrangular foramen or lateral axillary hiatus (long head of
triceps, teres major and minor)
Site of Entrapment
of Radial
Lateral intermuscular septum
Arcade of Frohse (supinator), leash of Henry (brachioradialis,
extensor carpi radialis brevis), Monteggia lesion
Superficial branch
Site of Entrapment
of Median
Ligament of Struthers (supracondylar process: medial
epicondyle)
Pronator teres muscle, sublimis bridge (flexor digitorum
sublimis), lacertus fibrosis
Gantzer’s muscle (flexor pollicis longus)
Transverse carpal ligament
Transverse metacarpal ligament
Site of Entrapment
of Ulnar
Arcade of Struthers (internal brachial ligament, medial head of
triceps, medial intermuscular septum)
Epicondylo-olecranon ligament, cubital tunnel retinaculum,
arcuate ligament of Osborne
Humeroulnar aponeurosis (flexor carpi ulnaris)
Deep flexor-pronator aponeurosis
Guyon’s canal (piso-hamate ligament, volar and transverse
carpal ligament
Deep branch
Transverse and oblique heads of adductor pollicis
Site of Entrapment
of L5 spinal
Iliolumbar ligament (fifth lumbar: wing of the ilium)
Site of Entrapment
of Ilioinguinal
Transverse abdominis muscle
Site of Entrapment
of Genitofemoral
Inguinal canal
Site of Entrapment
of Lateral femoral cutaneous
Inguinal ligament at anterior superior iliac spine
Site of Entrapment
of Femoral
Iliopectineal arch
Hunter’s canal (vastus medialis, adductor longus, sartorius), subsartorial canal
Infrapatellar branch of saphenous nerve
Site of Entrapment
of Obturator
Obturator canal
Site of Entrapment
of Sciatic
Pyriformis muscle
Greater and lesser sciatic foramens, sciatic notch, Gibraltar of the gluteus
Site of Entrapment
of Common peroneal
Fibular neck, peroneus longus muscle
Crural fascia, superficial branch
Inferior external retinaculum (ligamentum cruciforme)
Syndrome of Site of Entrapment of Brachial plexus
Anterior scalene syndrome
Costoclavicular syndrome
Hyperabduction syndrome
Thoracic outlet syndrome
“Rucksack” palsy
Syndrome of Site of Entrapment of Axillary
Quadrilateral space syndrome
Syndrome of Site of Entrapment of Radial
“Saturday night” palsy, “honeymooners’”
palsy
Supinator syndrome, posterior interosseous
syndrome, radial tunnel syndrome, tardy
radial palsy, “tennis elbow,” “frisbee flinging”
Cheiralgia paresthetica, Wartenberg’s disease,
“hand-cuff” or “wristwatch” neuropathy
Syndrome of Site of Entrapment of Median
Pronator syndrome, flexor digitorum sublimis syndrome
Anterior interosseous syndrome, Kiloh-Nevin
syndrome
Carpal tunnel syndrome
Intermetacarpal tunnel syndrome, “bowlers’
thumb”
Syndrome of Site of Entrapment of Ulnar
Cubital tunnel syndrome
“Tardy” ulnar palsy
Ulnar tunnel syndrome, “cyclists’” palsy
(Radfahrerlahung)
Piso-hamate hiatus syndrome
Syndrome of Site of Entrapment of T2–6 posterior rami
Notalgia paresthetica
Syndrome of Site of Entrapment of L5 spinal
Lumbosacral tunnel syndrome
Syndrome of Site of Entrapment of Lateral femoral cutaneous
Meralgia paresthetica, Roth’s meralgy,
Bernhardt’s syndrome
Syndrome of Site of Entrapment of Femoral
Iliacus tunnel syndrome
Gonyalgia paresthetica, “housemaids’ knee”
Syndrome of Site of Entrapment of Obturator
Howship–Romberg syndrome
Syndrome of Site of Entrapment of Sciatic
Pyriformis syndrome
Syndrome of Site of Entrapment of Common peroneal
“Cross leg” palsy
(Anterior) tarsal tunnel syndrome
Site of Entrapment of Posterior tibial
Canal calcaneen de Richet (ligamentum laciniatum)
Medial plantar nerve
Medial plantar proper digital nerve
Transverse metatarsal ligament
Syndrome of Site of Entrapment of Posterior tibial
(Posterior) tarsal tunnel syndrome
“Joggers’ foot,” abductor hallucis tunnel
syndrome
Joplin’s neuroma
Morton’s neuroma (metatarsalgia)
PATHOLOGY of CARPAL TUNNEL SYNDROME
carpal tunnel is at the base of the hand. The
carpal, or wrist bones, form the floor of the tunnel and the flexor retinaculum forms the roof. Nine flexor tendons also pass through the tunnel. Due to this crowded arrangement,
any tenosynovial proliferation, fluid collection, or arthritic
deformity can lead to carpal tunnel syndrome.
Pressure in carpal tunnel increases several fold with
wrist extension or flexion. In those with carpal tunnel syndrome, pressures can reach over 100 mmHg in flexion or extension, pressures high enough to impede flow to the arteries supplying the nerve, causing epineural ischemia. At somewhat lower pressures, venous return can be reduced, resulting in venous
stasis and intraneural edema.
SYMPTOMS of CARPAL TUNNEL SYNDROME
Classically, patients report numbness on the palmar surface of the thumb and index, middle, and half of the ring finger. fifth finger is spared
Carpal tunnel syndrome can cause pain.
The pain can be both distal and proximal to the site of compression. Patients can report pain in the hand, wrist, elbow, and shoulder.
Pain and numbness may increase when the wrist is
flexed or extended.
“flick sign” of Carpal tunnel syndrome
patients often report
symptoms at night when they awake after sleeping with their wrists in flexion. Many patients will report needing to shake their hand on waking to relieve their numbness
Carpal tunnel syndrome Patients usually do not complain of weakness
They may report dropping things or having difficulty with certain motor activities like doing up buttons or opening a jar.
These complaints are probably the result of a combination of mild thenar weakness and sensory loss.
Median Nerve Innervations
The median nerve after it exits the carpal tunnel supplies sensation to the palmar surface of the thumb and index, middle, and half the ring finger. It also supplies the dorsal
tips of these same fingers. Also the median nerve after exiting the carpal tunnel innervates a number of intrinsic hand muscles
The palmar branch of the median nerve spared in carpal tunnel syndrome.
supplies sensation to the proximal portion of the palm and thenar eminence, does not go through the
carpal tunnel, and is therefore
Two-point discrimination and pinprick testing will
often elicit
sensory deficits in parts of the median sensory
territory.
To test the strength of the abductor pollicis brevis
the patient should place the thumb perpendicular
to the plane of the hand and then resist as the examiner attempts to push the thumb into the plane of the hand. In most patients, weakness will only be appreciated when compared to the unaffected hand or to the flexor pollicis longus muscle of the affected side
Phalen’s maneuver
increases pressure by putting the patient’s wrist in hyperextension or hyperflexion. Most patients with carpal tunnel syndrome will report numbness, tingling, or pain
within 60 sec of the wrist being placed in extension or flexion.
Tinel’s sign
involves tapping over the carpal tunnel to elicit brief symptoms. It should be noted that brief
symptoms can be elicited in anyone if the tapping is vigorous enough.
Very sensitive for confirming a diagnosis of carpal tunnel syndrome.
Electrodiagnostic testing. The hallmark of electrodiagnosis is a delay in the distal latency of median nerve conduction.
This suggests a conduction delay through the carpal
tunnel.
The first line of treatment for carpal tunnel syndrome is
splinting to maintain the wrist in a neutral position and thereby minimize the pressure in the carpal tunnel. Splints should be worn both day and night. Anti-inflammatory
treatments including steroid injection benefit some select patients. Should conservative measures fail, then surgical
decompression is indicated
RISK FACTORS of
Carpal tunnel syndrome
repetitive stress injuries that occur with computer use. any occupation that requires repeated flexion and extension at the wrist
Others: obesity, arthritis, diabetes, and hypothyroidism. Square wrists, that is, those whose dorsal-volar distance is close to the medial-lateral distance with a ratio greater than 0.7
ULNAR NEUROPATHY
Entrapment
can occur either at the ulnar groove or at the cubital tunnel.
The ulnar nerve is particularly vulnerable to compression or stretch as it
crosses the elbow and passes through the
cubital tunnel.
The ulnar groove
formed by the medial epicondyle and the olecranon process. The ulnar nerve runs through
this groove as it crosses the elbow. The groove is easily palpable when the arm is extended at the elbow. As the elbow is bent, the groove disappears and the ulnar nerve is relatively superficial.
tardy ulnar palsy
Patients with a remote history of supracondylar fracture can develop such a bony deformity
and nerve impringement
Just distal to the elbow, as the ulnar nerve leaves the ulnar groove, it travels
under a ligamentous band that stretches from the medial epicondyle to the olecranon of the ulna
and then blends into the aponeurosis of the two heads of flexor carpi ulnaris muscle. This humeroulnar aponeurotic
arcade or cubital tunnel can be from 0.5 cm to
2 cm distal to the medial epicondyle, or end of the
ulnar groove. Pressure in the cubital tunnel can increase as the elbow is flexed.
SYMPTOMS of ULNAR NEUROPATHY
Intermittent numbness and tingling in the distribution of the ulnar nerve is usually the first symptom of ulnar palsy.
Patients can wake up with elbow pain radiating into the fifth digit. There can be cramping and aching in the hypothenar eminence. Symptoms can be exacerbated by flexion
of the elbow. Patients may complain about a generalized loss of strength in the hand or loss of dexterity.
The ulnar nerve supplies sensory fibers to the
fifth finger, both palmar and dorsal surfaces, and usually half of the ring finger. Sensory deficits that split the ring finger
are classic for an ulnar nerve injury.
sensitive for detecting
ulnar sensory deficits than pinprick or temperature
testing.
Light touch and two-point
discrimination
The ulnar sensory territory ends
proximally at about the
wrist crease.
ulnar half of the forearm is supplied by
the medial antebrachial cutaneous nerve, a branch of the brachial plexus. This area should not be involved in ulnar lesions at the elbow.
Ulnar injury can weaken
grasp and pinch strength.
the easiest muscles in ulnar injury to test directly are
the first dorsal interosseous and the abductor digiti minimi. The
hands are placed on a flat surface and the patient is asked to spread the fingers apart and resist the examiner’s attempt to bring the fingers closer together. Atrophy of
the hypothenar eminence and the first dorsal interosseous can often be seen. Clawing of the ring and little finger is
common in chronic cases.
can often elicit tenderness and help to localize the ulnar lesion
Palpation of the ulnar groove and over the cubital tunnel. Flexion of the elbow beyond 90 degrees can often provoke sensory complaints or pain
confirm a diagnosis of ulnar neuropathy and to exclude other causes including brachial plexopathy,
cervical radiculopathy, and an ulnar entrapment at the wrist
Electrodiagnostic testing. Nerve conduction studies will usually show slowing across the elbow and sometimes a drop in response amplitude
across the elbow. Inching techniques can sometimes localize the site of compression to the ulnar groove or the cubital
tunnel.
ulnar palsy at the elbow can be successfully
treated with
an elbow pad to reduce trauma to the nerve or
by avoiding prolonged flexion at the elbow. More severe cases may require surgery. The precise site of entrapment will determine the surgical procedure, which can include
transposition of the nerve, decompression at the aponeurosis, or even medial epicondylectomy.
RISK FACTORS for ulnar palsy
Resting a bent elbow on a hard surface is a behavior that can provoke ulnar palsy.
Various structures in the thoracic outlet can be the source of compression or impingement in thoracic outlet syndrome
A cervical rib is the most
discussed source of compromise in thoracic outlet syndrome. An anomalous fibrous band from the transverse process of the last cervical vertebra to the first rib is a common cause of impingement. Entrapments by the scalenes, subclavius, and pectoralis minor muscles have all been reported. Hyperextension injuries of the neck can lead to intrascalene muscle hemorrhage and swelling with resultant scar formation in the muscle or around the brachial plexus.
Most commonly in neurogenic thoracic outlet syndrome
the lower trunk of the brachial plexus is most involved
In thoracic outlet syndrome, Vascular syndromes usually involve
compromise of the axillary
and subclavian vessels.
The symptoms of thoracic outlet syndromes depend on
whether they are primarily arterial, venous, or neurologic and can vary with shoulder position
In thoracic outlet syndrome the arterial form, symptoms are
ischemic in nature
and include pain, paresthesias, coldness, and color change. Some patients complain of fatigue and soreness in the arm
In thoracic outlet syndrome the venous form, symptoms are
swelling, and cyanosis, as
well as pain and paresthesias.
In thoracic outlet syndrome the neurologic form, symptoms are
numbness of the medial forearm and ulnar side of the hand. This can be followed by an aching pain, poorly localized in the arm and anterior chest. Later patients may complain of clumsiness or weakness in the hand and fingers. Atrophy of both the thenar and hypothenar eminences can be seen
In thoracic outlet syndrome elicit symptoms
Anterior flexion of the shoulders. Abduction and supination of the arm can also elicit symptoms.
Certain activities that affect shoulder position can exacerbate the symptoms, such as carrying a heavy briefcase,
combing one’s hair, or using a mouse.
Symptoms of neurogenic thoracic outlet syndrome
usually affects the lower trunk of the brachial plexus first, which results
in sensory deficits on the ulnar side of the hand with
weakness and atrophy of the thenar eminence. As the syndrome progresses, sensory loss can involve all five fingers. True neurogenic thoracic outlet syndrome initially causes weakness of median innervated hand muscles
and later ulnar innervated muscles. Atrophy of both
thenar and hypothenar eminences can occur.
Symptoms of Vascular thoracic outlet syndrome
usually does not cause loss of strength, but arm and hand muscles may fatigue with use. Vascular compression can cause diffuse but usually
only subjective sensory deficits. Swelling, color changes, and temperature differences can all be seen
Adson’s maneuver
involves extending the arm at shoulder height to
the side and supinating the hand. The manuever can elicit both signs, that is, loss of radial pulse, and an increase in
sensory symptoms.
Elvey maneuver
stresses the brachial
plexus by again extending the arm to the side and then tilting the head to the opposite side. This maneuver stretches
the plexus on the side of the extended arm and in neurogenic thoracic outlet syndrome will provoke symptoms on that same side.
electrodiagnostic study of thoracic outlet syndrome
Early neurogenic thoracic outlet syndrome often presents with a normal electrodiagnostic study. One of the first electrodiagnostic abnormalities seen is a reduction in the amplitude of the medial antebrachial cutaneous sensory response. Later ulnar sensory responses in the
hand will be diminished. Late responses such as F-waves will become prolonged and conductions across the plexus will be slowed as plexopathy progresses. Needle examination
may elicit denervation changes in both median
and ulnar innervated hand muscles in advanced cases.
Treatment of thoracic outlet syndrome
Manipulations of shoulder
Correction of shoulder posture can improve if not completely eliminate the symptoms of thoracic outlet syndrome in many cases. Exercises that strengthen the rhomboid and trapezius muscles can improve shoulder posture. Clavicle straps can help maintain correct shoulder posture. The most common surgical procedures are resection
of cervical rib and fibrous band, and scalenectomies. Both procedures carry significant morbidity.
Treatment of thoracic outlet syndrome
Injections
The injection of botulinum toxin into the scalene muscles has been shown to be effective in some cases of thoracic
outlet syndrome. Other muscles, including subclavius, pectoralis minor, trapezius, and levator scapula also have been injected with good results
Potential complications of botulinum toxin injections in this area
dysphagia, dysphonia, and muscle weakness.
Activities that promote poor shoulder posture can provoke thoracic outlet syndrome
seen in professional musicians who play string instruments, nursing mothers, and computer users, especially on the side that operates the mouse. Bony deformities from clavicular fracture, cervical ribs, and sloped shoulders all predispose one to thoracic outlet syndrome. Recent trauma to the shoulder or neck,
even without fracture, can predispose a patient to thoracic outlet syndrome.
MERALGIA PARESTHETICA
Entrapment of the lateral femoral cutaneous nerve of the thigh.
Path of The lateral femoral cutaneous nerve
The lateral femoral cutaneous nerve of the thigh arises from upper lumbar roots, travels through the pelvis, and exits into the leg at the upper lateral end of the inguinal ligament. The nerve is usually trapped as it passes under or
through the inguinal ligament. Blunt trauma to this area can cause damage to the nerve.
Pathology of MERALGIA PARESTHETICA
More chronic episodic
external compression from tight-fitting clothes, a holster, or tool belt can provoke meralgia. However, entrapment
most often is related to increased intra-abdominal pressure from weight gain or pregnancy. Mass lesions, including
lipomas and fibroids
SYMPTOMS of MERALGIA PARESTHETICA
Patients complain of unpleasant sensations and numbness in the lateral thigh. Light touch in the area can be unpleasant. Even clothing or touching the area can be unpleasant. Walking, standing, or lying flat can sometimes exacerbate symptoms.
PHYSICAL FINDINGS of MERALGIA PARESTHETICA
The lateral femoral cutaneous nerve is a purely sensory nerve that supplies just the lateral thigh. Therefore, findings
are completely sensory. Sensory loss can be identified in a portion of the distribution of the nerve, usually the area
that the hand touches when it’s in the pants pocket.
ELECTRODIAGNOSIS of MERALGIA PARESTHETICA
It can be technically difficult to elicit sensory responses from the lateral femoral cutaneous nerve in
normal individuals. This makes interpretation of a lost or diminished response suspect
RISK FACTORS of MERALGIA PARESTHETICA
Obesity, pregnancy, diabetes, and tight-fitting clothes, Pelvic osteotomy and use of stabilization devices during spine
surgery
TREATMENT of MERALGIA PARESTHETICA
Pain control with medication is the standard treatment. Symptoms resolve within 6 months for the vast majority of patients using only these
conservative measures. Nerve blocks have been successful in some cases. There are also some reports of successful
treatment with pulsed radiofrequency. The utility of surgical intervention remains limited.
tarsal tunnel syndrome
used to describe entrapment of the posterior tibial nerve at the medial ankle
PATHOLOGY of tarsal tunnel syndrome
The tarsal tunnel is formed by the ankle bones and the flexor retinaculum. Through the tunnel passes the posterior tibial nerve, tendons of the foot and toe flexors, and the posterior tibial artery. Increased pressure in the tunnel brings on the syndrome.
tarsal tunnel syndrome can occur from
an ankle fracture or sprain, arthritic changes, tenosynovitis, or fluid
collection. Mass lesions in the tarsal tunnel like ganglion cysts or convoluted blood vessels, can also lead to compression of the posterior tibial nerve.
SYMPTOMS of tarsal tunnel syndrome
The primary complaint is foot pain, often described as burning. Many patients will isolate the burning to the sole of the foot. Painful numbness will often disturb sleep.
Walking and standing can exacerbate symptoms.
The posterior tibial nerve has three branches
calcaneal, medial plantar, and lateral plantar
PHYSICAL FINDINGS of tarsal tunnel syndrome
Intrinsic foot muscles primarily toe flexors
and abductors, can be affected but clinical testing of these muscles can be difficult. Motor findings, including weakness
and atrophy, are therefore usually evident only late in
tarsal tunnel syndrome. Pressure over the affected tarsal tunnel is usually painful. Eversion and dorsiflexion can also provoke symptoms.
ELECTRODIAGNOSIS of tarsal tunnel syndrome
Nerve conduction studies can reveal both motor and sensory
slowing through the tarsal tunnel. The syndrome is usually unilateral so comparisons with the unaffected side
make electrodiagnosis easier. Needle examination of intrinsic
foot muscles can be misleading. Some 10% to 20% of normal intrinsic foot muscles may demonstrate denervation
changes, that is, fibrillations and positive waves, as a result of direct muscle trauma from walking.
TREATMENT of tarsal tunnel syndrome
Anti-inflammatory medication can be useful in certain cases in which tenosynovitis or arthritis is suspected. Surgical
decompression is highly effective
RISK FACTORS of tarsal tunnel syndrome
Ankle trauma even if remote is common in tarsal tunnel syndrome. Rheumatoid arthritis and diabetes mellitus both increase the risk for tarsal tunnel syndrome.
INTERDIGITAL NEUROPATHY
(MORTON’S NEUROMA)
Pressure on an interdigital nerve in one of the intermetatarsal
spaces can cause pain and numbness in the distal foot and toes.
The interdigital nerves are
distal branches of the lateral and medial plantars.
The interdigital nerves are vulnerable to
chronic pressure and trauma between the metatarsal heads, against the transverse metacarpal ligament. At times, an actual scar, or neuroma, will form. This most commonly occurs between the third and fourth metatarsal heads but can involve other interdigital nerves
SYMPTOMS of INTERDIGITAL NEUROPATHY
The primary complaint is burning pain in the ball of the foot that radiates to one or two toes. The corresponding
toes may feel numb. Pain will be worse with weight bearing.
PHYSICAL FINDINGS of INTERDIGITAL NEUROPATHY
Pain can be elicited by pushing on the ball of the foot over the affected interdigital nerve. At times altered sensation can be demonstrated on the adjoining sides of the affected toes, though this can often be difficult or nonreproducible.
Electrophysiologic studies of the interdigital nerves
difficult and often unreliable. Both orthodromic and antidromic sensory or mixed nerve studies using both surface electrodes and near-needle electrodes have been described, but none are routinely performed
TREATMENT of INTERDIGITAL NEUROPATHY
Conservative measures including physical therapy, orthotics,
and avoiding offending footwear are often successful. Interdigital anesthetic nerve blocks, often with corticosteroids,
have been effective in some patients.
Surgical Treatment of INTERDIGITAL NEUROPATHY
Now neurolysis of
the interdigital nerve or removal of the neuroma (neurectomy) are the most common surgical options. The larger the neuroma, especially if it is greater than 5 mm
across, the more likely neurectomy is to be successful. Surgical risks include permanent loss of sensation and recurrent neuroma.
RISK FACTORS of INTERDIGITAL NEUROPATHY
Activities that increase trauma to the foot can all increase one’s risk for interdigital neuropathy. Ill-fitting shoes, especially
high heels, also predispose one to develop Morton’s neuroma.
