Neuropathies and Spinal Cord Lesions Flashcards
What are the cervical myotomes?
C5 - shoulder abduction and adduction, elbow flexion C6 - elbow flexion and wrist extension C7 - elbow extension, wrist flexion C8 - wrist flexion, finger flexion T1 - finger abduction
What myotomes are the biceps and brachioradialis reflexes?
C5 and C6
What myotome is the triceps reflex?
C7
What are the lumbosacral myotomes?
L2 - hip flexion and adduction
L3 - hyp adduction and knee extension
L4 - knee extension, foot inversion and dorsiflexion
L5 - hip extension and abduction, knee flexion, great toe dorsiflexion
S1 - knee flexion, foot plantarflexion and eversion
What are the myotomes for the lower limb reflexes?
Knee - L3/4
Great toe - L5
Ankle - S1
What is the common cause of spinal cord disease in 16-30 yo.?
Likely trauma of C4/5 or C5/6
What is the common cause of spinal cord disease in 30-50 yo.?
Likely disc disease of C5/6 or L4/5 or L5/S1
What is the common cause of spinal cord disease in 40+ yo.?
Likely malignancy
What are the potential causes of spinal cord problems?
Trauma Iatrogenic Osteoporosis Corticosteroid use Osteomalacia Osteomyelitis Tumour infiltration Disc herniation Infection
How do spinal cord problems present?
Back pain Numbness and paraesthesia Weakness and paralysis Bladder and bowel dysfunction Hyper-reflexia Spinal shock Neurogenic shock
What happens in spinal shock?
Loss of reflexes, tone and motor function
What happens in neurogenic shock?
Following cervical or high thoracic injury
Bradycardia, hypotension, warm dry extremities, peripheral vasodilation, venous pooling, priapism, low cardiac output
When should a CT C Spine <1hr be considered?
GCS < 13 Intubated >65yo High impact injury Focal neurological deficit Paraesthesia of UL or LL
How is Spinal cord compression managed?
Immobilise C spine - collar and backboard
Intubate if above C5
Decompressive surgery
Supportive management - VTE prophylaxis, maintain vitals, nutrition, catheter, laxatives, pressure sore prevention
If malignancy - palliative
Abscess - IV Vancomycin, metronidazole and cefotaxime + surgery
What are the ascending tracts?
Take sensory information from the body to the brain
Dorsal columns - posterior spinal cord - fine touch, vibration, proprioception
Decussate at the medulla
Spinothalamic tracts - anterior part of spinal cord - pain and temperature
Decussate immediately, ascend contralaterally
What are the descending tracts?
Motor information from UMNs to muscles
Pyramidal - conscious control, extrapyramidal - unconscious, reflexive
Pyramidal - corticospinal tract and corticobulbar tract
Extrapyramidal - reticulospinal, vestibulospinal, rubrospinal and tectospinal
All originate in the brainstem, carry motor fibres for unconscious responsive movements.
What is the corticospinal tract?
Communicates with primary motor cortex, premotor cortex, supplementary motor cortex
Converges in internal capsule, then divides into lateral and anterior tracts
Lateral decussates in medulla, anterior ipsilateral
What is the corticobulbar tracts?
From primary motor cortex and terminate in the brainstem at the motor nuclei
Then synapse onto cranial nerve motor nuclei - LMNs to supply the head and neck
What are the signs of UMN lesions?
Hypertonia Spastic Fasciculations absent Minimal atrophy Exaggerated reflexes/clonus Babinski's sign present
What are the signs of LMN lesions?
Hypotonia Flaccid Fasciculations present Marked atrophy Diminished reflexes Absent Babinski's
What is the pathophysiology behind the difference in UMN and LMN damage?
Impaired ability for motor neurones to regulate descending signals, so gives disordered spinal reflexes.
Corticospinal tract can help in conscious inhibition - if sever UMNs, there is loss of inhibitory tone of muscles
No LMN inhibition leads to LMN activation and constant contraction of muscles, sensory info not received so body thinks we are not compensating. No UMN to inhibit LMN anymore - lots of firing.
Initial flaccid paralysis then hypertonia, hypereflexia.
If LMNs damaged or lost, nothing to tell muscles to contract, so hypotonia and flaccid paralysis.
How do UMN and LMN lesions differ in the face?
Upper half of the face receives bilateral cortical supply, so UMN damage forehead is spared
Lower half receives contralateral cortical supply
What is decerebrate and decorticate posturing?
Decerebrate posturing - upper limb extension, a lesion below the red nucleus prevents the red nucleus from activating upper limb flexors
Decorticate posturing - upper limb flexion - a lesion above the red nucleus prevents inhibition of the red nucleus so there is flexion of the upper limb
What is the red nucleus?
In the rostral midbrain involved in motor coordination
Pale pink due to iron - Hb and ferritin
What are the types of ascending tracts?
Dorsal column-medial lemniscus - vibration, proprioception, fine touch
= fasciculus gracilis (below T6-T8) and fasciculus cuneatus (above T6-T8 but not the head)
Spinothalamic tract (anterolateral system) anterior - crude touch and pressure, lateral - pain and temp
Spinocerebellar tracts - transmits proprioceptive signals from body to brain
Where do the nerve fibres cross in the spinothalamic tract?
At the anterior grey commissure at the level of the spinal nerve
How can you clinically assess the ascending tracts?
Dorsal columns - vibration with 128Hz tuning fork, joint proprioception with small-joint movement, light touch - cotton wool
Spinothalamic tracts - pain with pin-prick, temp - cool and warm metal object
What are some of the signs that the lesion is within the spinal cord?
Mixed upper and lower neurone signs - as affects CNS (UMNs) and spinal nerves leaving SC (LMNs)
Sensory level - well demarcated, e.g. at T10 = umbilicus
Sphincter involvement - disruption of urinary or bowel function
Autonomic dysfunction/dysreflexia - indicates lesion is above T6
What are the signs of autonomic dysreflexia?
Hypertension Bradycardia Urinary retention Constipation Sweating Flushing above level of the lesion
What signs can help suggest where in the spinal cord is the problem?
If all four limbs - likely cervical
If only lower limbs - thoracic
Respiratory difficulties and diaphragm affected - avoe C3
What occurs in complete transection?
Interruption of all ascending and descending tracts bilaterally
Results in bilateral loss of motor function, complete loss of all modes of sensation below level of the lesion
What is seen in Brown-Sequard syndrome?
Damage to one lateral half of the spinal cord
Most commonly occurs in the cervical region
Spastic paralysis and loss of pain, temp, sensation in one leg (corticospinal and spinothalamic tracts)
Loss of fine touch, proprioception and vibration sense in the other
Dorsal columns ascend ipsilaterally, so lesion will be on same side of body as dorsal column symptoms
What is seen in anterior cord syndrome?
Front of spinal cord is damaged, but posterior part is spared
There is only one anterior spinal artery - blockage can damage whole anterior part - stroke within spinal cord
Causes bilateral disruption to spinothalamic tracts - bilateral loss of pain and temp sensation
Affects corticospinal tracts - bilateral spastic paralysis, UMN signs
Dorsal columns unaffected as are posterior - so fine touch, proprioception and vibration sensation preserved
What occurs in posterior cord syndrome?
Bilateral damage to the dorsal columns, affects fine touch, proprioception, vibration sensation
Corticospinal tracts can be affected, spinothalamic tracts are spared
Often seen in subacute combined degeneration
As a result of B12 deficiency
What is syringomyelia?
Central cord syndrome
Due to fluid filled cyst - syrinx around spinal canal
Associated with Chiari malformation
Decussating fibres first affected, then can expand and affect corticospinal and spinothalamic tracts
Upper limbs affected first, white matter fibres first to be compressed - cape like loss of pain and temp sensation
What is spinal cord concussion?
Transient loss of spinal cord function, usually resolving within 48 hours
What are the investigations for spinal cord lesions?
FBC U&Es LFTs B12 Inflammatory markers ESR or CRP Antibody screens - aquaporin 4/MOG (neuromyelitis optica)
MRI spinal cord, full spine
Infective or autoimmune consider an LP
What is a mononeuropathy?
Damage/dysfunction of a single peripheral nerve
Commonly due to entrapment or compression - internal e.g. tumour or external e.g. fracture, compressive clothing
What is the organisation of the peripheral nervous system?
Visceral fibres - sensory fibres that carry info from thoracic and abdominal compartments, and motor fibres forming ANS (sympathetic and parasympathetic)
Somatic fibres - important sensory info from skin, muscles, bone, joints
Motor and sensory somatic fibres carried via spinal nerves and cranial nerves
What are the three groups of mononeuropathies?
Cranial mononeuropathies - the 12 paired nerves arising from brain/brainstem
Upper limb
Lower limb
What is the median nerve innervation to the hand?
Sensory to palmar and distal dorsal aspects of lateral three and a half digits and palm
Motor function - Pronator teres Flexor carpi radialis Palmaris longus Flexor digitoris superficialis
Anterior interosseous - pronator quadratus, flexor pollicis longus, some of flexor digitorum profundus
LOAF - lumbricals, opponens pollicis, abductor pollicis brevis, flexor pollicis brevis
What can cause median nerve neuropathy?
Carpal tunnel syndrome - compression when passes through carpal tunnel and flexor retinaculum/carpal bones
Compression due to haematoma, trauma or tumour
Pronator teres syndrome
Anterior interosseous nerve syndrome - cannot make the ok sign
What are the risk factors for carpal tunnel syndrome?
Diabetes pregnancy Rheumatoid arthritis Obesity Thyroid disease
What are the features of median nerve neuropathy?
Sensory loss and/or paraesthesia over palmar/distal dorsal aspects of first 3 digits
Weakness/clumsiness using the hand
Weak thumb abduction
Thenar eminence wasting
Hand pain - typically worse at night
What manoevres can be performed to elicit signs of median nerve neuropathy?
Phalen’s
Tinel’s non specific, tapping proximal to damaged nerve, pain or paraesthesia over distribution of the median nerve
What is the anatomy of the ulnar nerve?
Continuation of medial cord of brachial C8-T1
Lies medial to brachial artery
At elbow, passes between medial epicondyle of humerus and olecranon of ulna
What can cause compression of the ulnar nerve?
Cubital tunnel at the elbow
Guyon’s canal at the wrist
What does the ulnar nerve innervate?
Sensory function to palmar and dorsal aspects of medial one and a half digits - little finger and medial side of ring finger
Flexor carpi ulnaris
Flexor digitorum profundus
Intrinsic muscles of the hand except for LOAF
What are the clinical features of ulnar neuropathy?
Sensory loss and/or paraesthesia
Hand weakness, loss of dexterity, grip weakness
Muscle wasting - hypothenar eminence
Claw hand deformity - hand of benediction secondary to an ulnar neuropathy
What is the presentation of radial neuropathy?
Acute wrist drop
Saturday night palsy
Sensory loss/paraesthesia over the dorsum of the hand
Weakness in finger extension
Weakness in brachioradialis
What is the presentation of axillary neuropathy?
Most often due to trauma e.g. shoulder dislocation
Regimental badge sensory loss
Supplies deltoid, teres minor, lateral head of triceps brachii
What is the presentation of common peroneal neuropathy?
Acute foot drop
Due to weakness of dorsiflexion
Commonly due to trauma/injury to the knee e.g. knee dislocation or from external compression
Sensory loss or paraesthesia over the dorsum of the foot and lateral shin
Weak dorsiflexion and eversion of the ankle
What is the presentation of tibial neuropathy?
Due to compression as it passes under the transverse tarsal ligament - fracture or dislocation of the ankle, inflammatory arthritis, tumours
Paraesthesia, pain and numbness over the sole of the foot
Pes planus, pronated foot or abnormal gait (antalgic gait, excessive pronation)
What are the investigations for mononeuropathies?
Electrodiagnostic testing
EMG - evaluates muscle units
NCS - evaluates peripheral nerves
Imaging - x-rays or CT, MRI if chronic
How can polyneuropathies be classified?
Onset:
Acute - GBS, vasculitis, toxins, critical illness
Chronic - DM, CKD
Pathology:
Demyelination - autoimmune, hereditary
Axonal degeneration - DM, Vit B12 deficiency
Presentation:
Motor - weakness, atrophy e.g. GBC, CMTD
Sensory - DM, CKD
Small or large fibre
What are some of the causes of polyneuropathy?
VITAMIN DC
Idiopathic DM Systemic illness Autoimmune - GBS Inflammatory - CIDP Toxic - alcohol, chemo Neoplastic - myeloma Hereditary - CMTD Nutritional - B12 Vasculitis Medications - nitrofurantoin, isoniazid
What are the investigations for polyneuropathies?
EMG testing
Nerve conduction studies
FBCs, U&Es, LFTs, Vits, myeloma screen, thyroid function, Hba1c, viruses, autoimmune, heavy metals, syphilis, Lyme’s
US, MRI, CT
Nerve biopsy, skin biopsy, autonomic testing, genetic testing
What are two important tests of ulnar function?
Froment’s - pinch piece of paper between thumb and index finger, if there is flexion of distal phalanx of thumb - suggests ulnar weakness
Wartenberg’s - hold fingers fully extended, if little finger drifts away this is positive, due to weakness of ulnar innervated third palmar interosseous muscle
What is the innervation from the radial nerve?
Sensory innervation for the dorsal aspect of the radial lateral three and a half digits
Triceps brachii
Extensor carpi radialis longus
Brachioradialis
Anconeus
Nerve passes through cubital tunnel into the forearm and continues as posterior interosseous nerve to innervate extensor muscles of forearm
What is saturday night palsy?
Heavily inebriated and place arm over a chair, leads to compression
Can also occur due to haematoma, trauma, tumour, diabetes, vasculitis
What is seen in isolated neuropathy of the posterior interosseous nerve?
Weak finger extension
Sparing of the proximal muscle groups
No sensory changes - it is a primary motor nerve
What muscles does the axillary nerve innervate?
Deltoid
Teres minor
Lateral head of the triceps brachii
What does the common peroneal nerve innervate?
Superficial peroneal nerve - anterolateral leg, lateral compartment of the leg
Deep peroneal nerve - first dorsal webspace, anterior compartment of the leg
What is meralgia paraesthetica?
Neuropathy of the lateral femoral cutaneous nerve
Over anterolateral thigh
Entrapment under the inguinal ligament, due to diabetes, obesity, old
Pain, numbness, paraesthesia over the anterolateral thigh
Solely sensory nerve, so reduced pin prick sensation on clinical testing, absent motor signs
What are the two major pathological mechanisms of polyneuropathy?
Demyelination - degeneration of the myelin sheath
Axonal degeneration - dying back phenomenon starts distally
What are the clinical features of a polyneuropathy?
Glove and stocking distribution
Burning sensation Paraesthesia Sensory loss - touch, pain, temperature Ataxia - poor coordination Loss of light touch, vibration, proprioception
Weakness, absent reflexes, hypotonia, fasciculations, muscle atrophy, cramping
What is the course of the oculomotor nerve?
Midbrain into subarachnoid space
To lateral wall of cavernous sinus
Divides into superior and inferior fibres in the superior orbital fissure
What are the stages of the pupillary light reflex?
Light source detected by photoreceptors
Transmitted via optic nerve
Input from pre tectal nucleus transmitted to the Edinger Westphal nuclei
From EWN to ciliary ganglion
From short ciliary nerve to ipsilateral pupillary sphincter
Pupillary constriction
What sort of lesions can cause a third nerve palsy?
Midbrain - tumour, haemorrhage, ischaemia
Subarachnoid space - inflammation, malignancy, ischaemia, aneurysm
Cavernous sinus - thrombosis, tumour, carotid artery aneurysm
What does pupil sparing versus pupil involvement tell us about third nerve palsies?
Parasympathetic fibres are superficially within the nerve
Compressive lesions e.g. aneurysms affect outer fibres leading to pupillary dilatation, loss of light reflex
Vascular lesions inner fibres preferentially so are sparing
What is a sixth nerve palsy?
Dysfunction of the abducens nerve, causing a lateral rectus palsy
What is the difference in presentation of an isolated abducens palsy between adults and children?
Adults - ischaemic mononeuropathy e.g. diabetes, hypertension
Children - tumours, trauma, increase in ICP, congenital lesion
What is the presentation of a sixth nerve palsy?
Failure in eye abduction leading to horizontal diplopia
Diplopia worse on horizontal gaze in direction of lesion
What are the features of L1 radiculopathy?
Sensory changes in inguinal region
What are the features of L2-L4 radiculopathy?
Acute back pain
Radiates down anterior thigh
Sensory changes over anterior thigh, medial lower leg
Weakness in hip flexion, knee extension, hip adduction
May have loss of knee reflex
What are the features of L5 radiculopathy?
Acute back pain
Radiates down lateral aspect of foot
Weakness in foot dorsiflexion, big toe extension, foot inversion/eversion
What are the features of S1 radiculopathy?
Acute back pain
Radiates down posterior aspect of leg into the foot
Sensory changes over posterior leg and lateral foot
Weakness in hip extension and knee flexion
May have loss of ankle reflex
What manoeuvres can help determine if pain is radicular in origin?
Straight leg raise for L5/S1 radiculopathy
Reverse straight leg raise for L2-4 radiculopathy - worsening radicular pain on extending leg with patient prone
What is sciatica?
Clinical manifestation of lumbosacral radiculopathies
Nerve roots L4, L5, S1, S2, S3
Pain radiates down posterior/lateral leg, to foot or ankle
What is seen in C5 radiculopathy?
Neck pain, shoulder and scapula
Sensory loss on lateral upper arm
Weakness of shoulder abduction
What is seen in C6 radiculopathy?
Neck pain, shoulder, scapula
Lateral arm, forearm, hand
Sensory loss in lateral forearm, thumb, finger (pointing a gun)
Weakness of elbow flexion, supination/pronation
What is seen in C7 radiculopathy?
Neck pain, shoulder, hand, middle fingers
Sensory loss in palm, middle and index finger
Weakness in elbow and wrist extension
Triceps reflex affected
What is seen in C8 radiculopathy?
Neck pain, shoulder, medial forearm, hand, 4th/5th fingers
Sensory loss in medial forearm, hand and 4/5th digits, weak finger movements
What signs can suggest the involvement of the cervical cord?
Lhermitte phenomenon
Gait disturbance
UMN signs in the lower limbs - increased tone, weakness, clonus, upgoing plantars
Bladder/bowel dysfunction
