Download Year 2004 Paper one: Questions supplied by Megan

Year 2004 Paper one: Questions supplied by Megan
QUESTION 47
A 58yo man is noted to have a right foot drop three days following a right total hip replacement. On
examination there is weakness of right ankle dorsiflexion and toe extension (grade 4/5). Other muscle
groups are normal. The knee jerks are symmetrical with an absent right ankle jerk. Sensation is reduced
on the sole and dorsum of the right foot.
The most likely diagnosis is:
A.
B.
C.
D.
E.
Femoral neuropathy
Sciatic neuropathy
L5 radiculopathy
Tibial neuropathy
Peroneal neuropathy
CAUSES OF FOOT DROP
-
Common peroneal nerve palsy
Sciatic nerve palsy
L4,L5 root lesion
Peripheral motor neuropathy
Distal myopathy
Motor neuron disease
Stroke
NERVES OF THE LOWER LIMB
Year 2004 Paper one: Questions supplied by Megan
Femoral Nerve:
-
Largest branch of the lumbar plexus
L2, L3, L4
Forms in the abdomen and runs through the pelvis and under the inguinal ligament
Runs lateral to the femoral vessels in the femoral triangle and outside the femoral sheath
Breaks up into several terminal branches
Supplies the anterior femoral muscles
Sends articular branches to the hip and knee joints
Gives several branches to the skin on the anteromedial side of the lower limb
Saphenous nerve (L2, L3, L4) is a cutaneous branch of femoral nerve
It descends through femoral triangle lateral to the femoral sheath
Then accompanies the femoral artery in the adductor canal and passes anteriorly to supply the
skin and fascia of the anterior and medial aspects of the knee, leg and foot
Knee reflex (L2, L3, L4)
Sciatic Nerve:
-
L4, L5, S1, S2, S3
Largest nerve in the body
Leaves the pelvis through the greater sciatic foramen
Runs deep to gluteus maximus but usually supplies no structures in gluteal region
Year 2004 Paper one: Questions supplied by Megan
-
Supplies all the hamstring muscles (mainly via tibial division but short head of biceps via common
peroneal division)
Tibial and common peroneal nerves usually separate in inferior part of thigh
Tibial nerve (L4, L5, S1, S2, S3) runs behind the knee in the popliteal fossa
Gives branches to the knee
Supplies gastrocnemius, plantaris, popliteus and soleus muscles (posterior compartment
muscles)
Divides into medial and lateral plantar nerves which supply the skin on the sole of the foot
Uncommonly injured but can occur with lacerations or posterior dislocations of the knee
Results in loss of plantarflexion and flexion of toes and loss of sensation over sole of foot
In the foot, all intrinsic muscles are supplied by branches of the tibial nerve except for flexor
extensor digitorum brevis which is supplies by the deep peroneal nerve
Ankle reflex S1, S2
Tibial nerve gives the medial sural cutaneous nerve which usually joins the communicating
branch of the peroneal nerve to form the sural nerve
Sural nerve (S1, S2) supplies the lateral aspect of the ankle and foot
Common peroneal nerve (L4, L5, S1, S2) runs down the medial border of the popliteal fossa
Gives branches to the knee
Gives off lateral sural cutaneous nerve which supplies the skin on the lateral aspect of the leg (L5,
S1, S2)
Also gives off the peroneal communicating branch which joins the medial sural cutaneous nerve
to form the sural nerve
Winds around the neck of fibula and runs down behind the peroneus longus muscle
Divides into superficial and deep branches
Deep peroneal nerve supplies the muscles of the anterior crural compartment, the ankle joint
nd
and the skin between the big and 2 toes (L4, L5)
The anterior compartment muscles are mainly involved in dorsiflexion of the foot and extension
of the toes
Superficial peroneal nerve (L5, S1, S2) supplies the lateral crural compartment muscles
These muscles (peroneal muscles) plantarflex and evert the foot
Superficial peroneal nerve also supplies an area of skin over the anterior aspect of the ankle, the
dorsum of the foot and most of the toes
A. Injury to the femoral nerve would result in weakness of knee extension and reduced knee jerk.
Would also lead to loss of sensation over anteromedial aspect of thigh and leg.
B. Sciatic neuropathy would results in weakness of knee flexion and all movements of the
ankle/foot. Also there would be loss of sensation of the posterior, lateral and medial areas of the
leg and all of the foot (ie. all areas below the knee except for that supplied by the saphenous
nerve). Note sciatic nerve is most likely to be injured with hip surgery.
C. L5 radiculopathy would result in loss of sensation over the dorsum of the foot and the
anterolateral portion of the leg. There may be some weakness of all the movements of the ankle
as L5 is involved in the supply to all 3 compartments and also to the feet.
D. Tibial neuropathy would lead to weakness of plantarflexion as it supplies the muscles of the
posterior crural compartment. Also loss of flexion of the toes and loss of sensation over the sole
of the foot.
E. Peroneal neuropathy results in weakness of dorsiflexion and extension of the toes. Loss of
sensation of the skin over dorsum of foot and toes and anterior aspect of lower leg. May also be
weakness of eversion due to involvement of superficial peroneal nerve.
This man has weakness of dorsiflexion and toe extension (deep peroneal nerve) but also has reduced
sensation on the sole (tibial nerve) and dorsum (peroneal nerve) of the foot. Absent ankle jerk indicates
Year 2004 Paper one: Questions supplied by Megan
the tibial nerve or S1, S2. Only the sciatic nerve is involved in all these processes so there must be a partial
lesion of this nerve.
Answer: B
Table 363–1. Common Mononeuropathies (from Harrisons)
Nerve
Origina
UPPER EXTREMITY
Suprascapular C5, C6
Muscles
Innervated
Usual Site of
Lesion
Clinical
Features
Comments
Supraspinatus
Weakness of
lateral rotation
of the humerus
Winging of
scapula
Weakness of
shoulder
abduction;
atrophy of
shoulder
Wrist drop most
obvious, also
finger and thumb
extensors
paralyzed
Finger drop;
wrist relatively
spared
No sensory deficit
Infraspinatus
Serratus anterior
Suprascapular
notch of
scapula
Variable
Weakness of
finger adduction
and abduction
and thumb
adduction (see
text);
interosseous
atrophy, clawhand
Same as above
May be acute or
insidious; sensory
symptoms/signs
are distinctive
(Figs. 22-2 and
22-3); see also text
Long thoracic
C5–C7
Axillary
C5, C6
Deltoid, teres
minor
Near shoulder
joint
Radial
C5–T1
Triceps,
brachioradialis,
wrist, finger, and
thumb extensors
Spiral groove
of humerus
Posterior
interosseous
branch
C7, C8
Finger and thumb
extensors
Ulnar
C8, T1
Ulnar flexor of
the wrist, long
flexors of 4th and
5th digits, and
most intrinsic
hand muscles
Edge of
supinator
muscle below
elbow
Ulnar groove
at the elbow
Cubital tunnel
Medial base of
palm
Median
C6–T1
Abductor pollicis
brevis; more
proximal muscles
include forearm
pronator, long
finger and thumb
flexors
Carpal tunnel
Anterior
interosseous
C7–T1
Long flexors of
thumb and index
Anterior
interosseus
Intrinsic hand
muscles only,
interosseous
atrophy
Characteristic
sensory
symptoms and
deficit and
inability to make
a circle with
thumb and index
finger
Weakness of
pinch; pain in
No sensory deficit
Sensory deficit
similar to C5
dorsal root lesion
(See Figs. 22-2
and 22-3)
Saturday night
palsy (acute
compression) is
frequent cause
No sensory deficit
Often pain over
medial proximal
forearm (cubital
tunnel)
No sensory deficit
Sensory deficit as
per Figs. 22-2 and
22-3 (see text);
known as carpal
tunnel syndrome
No sensory deficit
Year 2004 Paper one: Questions supplied by Megan
branch
LOWER EXTREMITY
L2–L4
Femoral
and middle
fingers
branch below
the elbow
volar forearm
Proximal to
inguinal
ligament
Knee buckling;
absent knee jerk;
weak anterior
thigh muscles
with atrophy
Dysesthetic
hyperpathia of
lateral thigh
Association with
diabetes mellitus;
sensory
disturbance as per
Fig. 22-2
Known as
meralgia
paresthetica
Intrapelvic or
at pubis
Near sciatic
notch
Weakness of hip
adduction
Severe lower leg
and hamstring
weakness; flail
foot; severe
disability
Pain and
numbness of
sole, weak toe
flexors
Sensory deficit on
medial thigh
Uncommon except
from war wounds;
sometimes after a
misdirected
injection
Known as tarsal
tunnel syndrome
(see text)
Foot drop and
weakness of foot
eversion
Sensory deficit is
similar in
distribution to L5,
S1 sensory roots
Lateral
femoral
cutaneous
branch
Obturator
L2, L3
Iliopsoas (hip
flexor) and
quadriceps
femoris (knee
extensor)
None
L3, L4
Thigh adductors
Sciatic
L4–S3
Posterior tibial
L5–S2
Peroneal
L4–S1
Hamstring
muscles, hip
abductor, and all
muscles below the
knee
Calf muscles
(proximally), toe
flexors, and other
intrinsic foot
muscles
Dorsiflexors of
toes and foot,
evertors of foot
a
Spinal segments.
Inguinal
ligament
Tarsal tunnel,
near medial
malleolus
At neck of
fibula