LESIONS OF PERIPHERAL NERVES

AND ROOTS

Peripheral nervous system

Part of nervous system outside CNS

Nerves from brain and spinal cord

PNS is divided into :1.Somatic

2.Autonomous

Somatic nervous system Nerves from cns to skeletal muscles

1.spinal nerve a. 8 pairs of cevical nerves b. 12 pairs of thoracic nerves c. 5 pairs of lumbar nerves d. 5 pairs of sacral nerves e. 1 pair of coccygeal nerves

Attached to spinal cord by 2 roots - dorsal and ventral roots

2. cranial nerves

Cell bodies in brain 12 pairs olfactory , optic , occulomotor ,

trochlear , trigeminal , abducens , facial , vestibulocochlear , glossopharyngeal , vagus , spinal accessory , hypoglossal nerves

Autonomic nervous system

Supply all tissues other than skeletal muscles

ANS is divided into – 1.sympathetic consisting of thoracic and

lumbar ganglia

2.parasympethetic consisting of III,VII,IX,X cranial nerves and 2, 3,4

sacral segments of the spinal nerves

Lesions of peripheral nerves and roots

Lesions/diseases affecting neve roots – radiculopathy

Lesions/diseases affecting nerve plexus- plexopathy

Lesions/diseases affecting individual nerves-

neuropathy

neuropathy

It can be of

a. focal affecting a single nerve – mononeuropathy

b.multifocal affecting several nerves – mononeuropathy multiplex

c.generalised - polyneuropathy

mononeuropathiesI. ENTRAPMENT NEUROPATHY Due to compression/or entrapment of

single nerve Pathology – presure damages myelin

sheath,axons and cause slowing of conduction

eg. median nerve – carpel tunnnel

syndrome ulnar nerve at elbow radial nerve compression common peroneal nerve compression lateraL cutaneous nerve of thigh

compression

NERVE MUSCLE WEAKNESS

AREA OF SENSORY LOSS

MEDIAN NERVE(CARPEL TUNNEL SYN.)

ABDUCTOR POLLICIS BREVIS

LAT PALM &THUMB,INDEX MIDDLE ,LAT HALF OF 4TH FINGER

ULNAR (AT ELBOW)

ALL SMALL HAND USCLES EXCLUDING APB

MEDIAL PALM,LITTLE AND MEDIAL HALF OF 4TH FINGER

RADIAL SUPINATORWRIST & FINGER EXTENSORS

DORSUM OF THUMB

COMMON PERONEAL

DORSIFLEXION AND EVERSION OF FOOT – FOOT DROP

DORSUM OF FOOT

LATERAL CUTANEOUS NERVE OF THIGH

NILLATERAL BORDER OF THE THIGH

II. TRIGEMINAL NEUROPATHY

Unilateral facial sensory loss

Associated with scleroderma,sjogren syndrome

Reactivation of varicella virus in trigeminal ganglion causes herpes zoster

.III. FACIAL NERVE PALSY

Also called bell’s palsy

Causes – lesion within facial canal or maybe due to reactivation of latent herpes simplex virus 1 infection

Symptoms – pain around ears unilateral facial weakness deviation of angle of mouth

.IV. HEMIFACIAL SPASM

Seen after middle age

Intermittent twitching around one eye spreading ipsilaterally to other parts of facial muscles

Spasms exacerbated by talking,eating or stress

Cause – an aberrant arterial loop irritating the nerve just outside the pons

Mononeuropathy multiplex Involvement of several isolated nerves Nerves involved are widely seperated

leading to asymmetrical pattern Clinical pattern resemble polyneuropathy Due to involvement of vasa nervosum or

malignant infiltration of nerves causes ; acute – DM,

vasculitis,diphtheria,lymes disease,cryoglobinemia

chronic – DM,leprosy,paraprotinaemia,HIV,sarcoidosis

polyneuropathy

Simultaneous involvement of many peripheral nerves

Symmetric and distal loss of functions

Distal lower limbs are involved first and later the distal upper limbs

Glove and stocking sensory loss

.I . GUILLAIN-BARRE SYNDROME

Syndrome of acute paralysis In 70%of patients within 1-4 weeks after

respiratory infection or diarrhoea Pathology – CMI responses directed at

myelin proteins of spinal roots and nerves

- due to mimicry between epitopes in micro organisms and gangliosides

Release of cytokines block nerve conduction

.Clinical features include

Distal paraesthesia & limb pain

Rapidly ascending muscle weakness

Facial and bulbar weakness

Ultimately respiratory weakness

.

II . CHRONIC POLYNEUROPATHY

Most frequent

Two types - chronic demyelinating polyneuropathy

– hereditary and immune mediated -chronic axonal polyneuropathy

Plexopathy

I . BRACHIAL PLEXOPTHY Trauma to the brachial plexus

Causes- infiltration from breat or apical lung tumour

-anatomical abnormalities According to site:- -upper plexus (root- C5/6) -lower plexus (root – C8/T1) -thoracic outlet syndrome (root – C8/T1)

SITE ROOT AFFECTED

MUSCLES

SENSORY LOSS

UPPER PLEXUS

(erb-duchenne syndrome)

C5/6BICEPS,DELTOID,SPINATI,RHOMBOIDS,BRACHIORADIAALIS

PATCH OVER DELTOID

LOWER PLEXUS

(dejerine-klumpke syndrome)

C8/T1ALL SMALL HAND MUSCLES,ULNARWRIEST FLEXORS

ULNAR BORDER HAND/FOREARM

THORACIC OUTLET SYNDROME

C8/T1 SMALL HAND MUSCLES,ULNAR FOREARM

ULNAR BORDER HAND/FOREARM/UPPERARM

.II . LUMBOSACRAL PLEXOPATHY

Causes – neoplastic infiltration compression by retroperitoneal

haematomas in patients with coagulopathy

Presents with painful wasting of quadriceps with weakness of knee extension and adduction, absent knee jerk

radiculopathy

Causes : - - compression at or near spinal exit

foramen by prolapsed intervertebral disc -degenerative spinal disease

-infiltration by spinal and paraspinal tumour masses

.Clinical features

Muscle weakness

Muscle wasting

Dermatomal sensory loss

Pain in the muscles whose motor roots are involved

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