J Rehabil Med 2008; 40: 879–881

Case Report

QUANTITATIVE ASSESSMENT OF ANAESTHETIC NERVE BLOCK AND
NEUROTOMY IN SPASTIC EQUINUS FOOT: A REVIEW OF TWO CASES
Corinne Bleyenheuft, MD1, Christine Detrembleur, PhD1, Thierry Deltombe, MD2,
Edward Fomekong, MD3 and Thierry M. Lejeune, MD, PhD1
From the 1Physical Medicine and Rehabilitation Department, Université catholique de Louvain, Cliniques universitaires
Saint-Luc, Brussels, 2Physical Medicine and Rehabilitation Department, Université catholique de Louvain,
Cliniques universitaires de Mont-Godinne, Yvoir, and 3Neurosurgery Department, Université catholique de Louvain,
Cliniques universitaires Saint-Luc, Brussels, Belgium

Objective: To quantitatively evaluate the effect of motor
nerve branch block and neurotomy of the soleus nerve on
triceps surae spasticity, reviewing 2 cases.
Methods: Beside clinical assessment, we carried out a quantitative measurement of the stiffness of the ankle flexor muscles. The path length of the phase diagram between elastic
and viscous stiffness quantifies the reflex response to movement and reflects the importance of the spasticity. The assessments were carried out before and 30 min after motor
nerve branch block of the upper soleus nerve and more than
7 months after neurotomy.
Results: Both patients presented with pronounced ankle
plantar flexor spasticity: their path lengths were more than
6 times greater than normal values at baseline (#1: 354 N
m rad–1; #2: 409 N m rad–1). Motor nerve branch block and
neurotomy allowed a near-normalization of elastic and visc­
ous stiffness of ankle plantar flexor muscles in the 2 patients.
Their path length was almost similarly improved by motor
nerve branch block (#1: 127 N m rad–1; #2: 231 N m rad–1)
and neurotomy (#1: 60 N m rad–1; #2: 162 N m rad–1).
Conclusion: These case reports highlight the fundamental
role of the soleus muscle in triceps surae spasticity in our
patients, the predictivity of motor nerve branch block in the
preoperative assessment, and the effectiveness of soleus neurotomy in spastic equinus foot.
Key words: nerve block, muscle spasticity, stoke.
J Rehabil Med 2008; 40: 879–881
Correspondence address: Corinne Bleyenheuft, Université
catholique de Louvain, Cliniques universitaires Saint-Luc,
Physical Medicine and Rehabilitation Department, Brussels,
Belgium. E-mail: corinne.bleyenheuft@uclouvain.be
Submitted March 6, 2008; accepted June 12, 2008
Diagnostic soleus motor nerve branch block (MNBB) with
anaesthetics is a method frequently used in patients after stroke
to assess the role of the soleus muscle in spastic equinus foot,
as described by Decq et al. (1). In the case of positive response
to MNBB, a partial neurotomy of the soleus nerve can be performed. In theory neurotomy has the same impact on spasticity as
MNBB; however, in clinical practice, the spasticity assessment
is unfortunately limited to ordinal scales with low reliability, as
shown by Platz et al. (2) in a recent systematic review. A quanti-

tative method, such as the one described by Lehmann et al. (3),
seems to be a reliable indication of ankle plantar flexor muscles
spasticity, as previously shown by Detrembleur & Plaghki (4)
and Deltombe et al. (5). The objective of this study was quantitatively to evaluate the effect of MNBB and neurotomy of the
soleus nerve on spasticity, reviewing 2 cases.
Methods
Clinical evaluation
Clinical assessment included the passive range of motion (ROM)
measurement of the ankle, Manual Muscle Testing (MMT) of the
ankle dorsal and plantar flexors (Medical Research Council scale),
and spasticity assessment with the Tardieu scale (6).
Quantitative assessment
The muscles can be modelled as a spring and a viscous damper connected in parallel. As a spring, the elastic stiffness of the muscle is independent of velocity and will produce a torque response in phase with
the displacement. As a damper, viscous stiffness increases with velocity
and will develop a resistive force in proportion to the velocity applied
to it. Elastic and viscous stiffness of the ankle plantar flexor muscles
can be assessed by a method described by Lehmann et al. (3). This
method was previously used by Detrembleur & Plaghki (4) to assess
the effect of intrathecal baclofen administration in 11 spastic patients.
The same experimental procedure was followed in this study.
Motor nerve branch block and neurotomy
Using 1.5 ml of 2% lidocaine, we performed MNBB of the upper nerve
of the soleus following the method described by Deltombe et al. (7).
A partial and segmental selective neurotomy of the soleus nerve was
performed following the method described by Decq et al. (8).
Subjects
The first patient was a 47-year-old woman with right spastic hemiparesis. Her Stroke Impairment Assessment Set (SIAS) (9) was 49/76.
She presented with a permanent ankle clonus, which impaired her
gait. She did not have any orthopaedic contracture; in particular, the
ROM of the ankle in dorsiflexion was above 0°, as shown in Table I.
We performed MNBB of the upper nerve of the soleus 2 months after
stroke, and the patient underwent surgery 16 months after stroke.
Given that the patient meanwhile developed a slight contracture of
the gastrocnemius muscles, we performed a combined surgery (80%
fascicular resection of the upper nerve of the soleus associated with
30% resection of the lower nerve of the soleus and slight lengthening of gastrocnemius muscles). Clinical evaluation and quantitative
assessment of spasticity were carried out before MNBB, 30 min after
MNBB, and 7 months after surgery.

© 2008 The Authors. doi: 10.2340/16501977-0263
Journal Compilation © 2008 Foundation of Rehabilitation Information. ISSN 1650-1977

J Rehabil Med 40

880

C. Bleyenheuft et al.

The second patient was a 68-year old man with a left spastic hemiparesis. His SIAS was 54/76. He also presented with a permanent ankle
clonus, which impaired gait, without any contracture (Table I). We performed MNBB of the upper nerve of the soleus 25 months after stroke,
and the patient underwent selective neurotomy (75% fascicular resection
of the upper nerve of the soleus) 32 months after stroke. Clinical evaluation and quantitative assessment of spasticity were carried out before
MNBB, 30 min after MNBB and 19 months after surgery.
This study was approved by the local ethics committee, and both
patients provided written informed consent.

Results
At baseline, both clinical evaluation and quantitative assessment
of ankle plantar flexor muscles stiffness demonstrated a marked
spasticity in the 2 patients (Table I and Fig. 1). The elastic and

viscous components of stiffness are shown as a function of oscillation frequency in Fig. 1A and 1B. Before treatment, elastic
stiffness followed an abnormal V-shaped curve, with maximum
values at the low and high frequencies of oscillation and minimal
values at intermediary frequencies. As stated earlier, this is not
normal; normal subjects exhibit elastic stiffness that is independent of velocity. Viscous stiffness also showed pathological results,
with higher values at high and low frequencies of oscillation
and lower values at intermediate frequencies (“S-shaped path”).
In normal subjects, viscous stiffness increases as a function of
velocity. The path length (Lpath) of the phase diagram between
elastic and viscous stiffness (Fig. 1C and Table I) quantifies the
reflex response to movement and reflects the importance of the
spasticity. Before treatment, the phase diagram followed a Cshaped path with abnormal high values for the Lpath.

Fig. 1. The left-hand graphs show data for patient 1 and the right-hand graphs for patient 2. For both patients, the 2 curves in the upper panels (A and
B) trace the time course of elastic and viscous stiffness of the ankle plantar flexor muscles expressed in N m rad–1 by oscillation in frequency (in Hz).
The lower panel (C) shows the phase diagram of viscous stiffness as a function of elastic stiffness. Circles (●) represent the median value for stiffness
before motor block. Squares (■) represent the median value for stiffness 30 min after selective motor block. Triangles (▲) represent the median value
for stiffness after neurotomy. The grey line is the median value for stiffness in normal subjects.
J Rehabil Med 40

Motor block and tibial nerve neurotomy
Table I. Clinical assessment and path length in the phase diagram
Before After
After
MNBB MNBB surgery*
Patient 1
Ankle ROM in dorsiflexion, knee flexed (°) 5
Ankle ROM in dorsiflexion, knee
0
extended (°)
Spasticity (Tardieu scale /4)
4
Manual Muscle Testing of ankle dorsal
2
flexors (/5)
Manual Muscle Testing of ankle plantar
1
flexors (/5)
Path length in the Phase Diagram
354
(N m rad–1)
Patient 2
Ankle ROM in dorsiflexion, knee flexed (°) 20
Ankle ROM in dorsiflexion, knee
10
extended (°)
Spasticity (Tardieu scale /4)
4
Manual Muscle Testing of ankle dorsal
5
flexors (/5)
Manual Muscle Testing of ankle plantar
2
flexors (/5)
Path length in the Phase Diagram
409
(Nm rad–1)

5
0

10
5

0
2

0
2

1

1

127

60

20
15

15
0

2
5

1
5

2

2

231

162

*Patient 1 = 7 months after surgery; Patient 2 = 19 months after surgery.
MNBB: motor nerve branch block; ROM: range of motion.

Patient 1 showed a clinical improvement in spasticity after
MNBB and after surgery, with a decrease in the Tardieu scale
value from 4/4 to 0/4 (Table I). Ankle ROM was improved
after surgery because of the associated orthopaedic gesture.
Quantitative assessment of spasticity confirmed our clinical
results. MNBB and neurotomy allowed a similar improvement
in elastic and viscous stiffness (Fig. 1A and 1B) with a normalization of the curves. C-shaped path and Lpath (Fig. 1C and
Table I) exhibited closer to normal values after MNBB (from
354 N m rad–1, 13.1 times normal value, to 127 N m rad–1, 4.7
times normal value) (4) and, slightly more importantly, after
surgery (60 N m rad–1, 2.2 times normal value).
Patient 2 had a slightly greater clinical improvement in
spasticity after neurotomy than after MNBB, with a decrease
in Tardieu scale from 4/4 to 2/4 after MNBB and to 1/4 after
neurotomy (Table I). Several months after surgery, we observed
a decrease in ankle ROM in dorsiflexion, which was more
significant when the knee was extended than when the knee
was flexed. Quantitative assessment of spasticity showed a
near-normalization of the elastic and viscous stiffness shape
curves (Fig. 1A and 1B) with a downward shift, almost similarly after MNBB and after surgery. C-shaped path and Lpath
(Fig. 1C and Table I) exhibited values closer to normal after
MNBB (from 409 N m rad–1, 6.1 times normal value, to 231 N
m rad–1, 3.4 times normal value) and, slightly more importantly,
after surgery (162 N m rad–1, 2.4 times normal value).
Discussion
Our results highlight the important contribution of the soleus
muscle to the spasticity of the plantar flexor muscles. The two

881

patients described here were quantitatively assessed in a knee
extended position, stretching both the soleus and gastrocnemius
muscles. Motor block and neurotomy of the motor nerve branch
to the soleus muscle allowed a normalization of elastic and visc­
ous stiffness of the triceps surae muscle in the first patient, and
results reaching closer to normal values in the second patient.
The predominance of the soleus muscle over gastrocnemius in the
pathogenesis of spastic equinus foot has already been described
by Decq et al. (1) and Buffenoir et al. (10). This predominance
can be explained by several histological and biomechanical
arguments. Additionally, this predominance has been illustrated
in a recent case report by Deltombe et al. (5). In this case report,
we carried out an objective evaluation of a simulated effect of
a motor block instead of a neurotomy on the spasticity of the
triceps surae muscle. To our knowledge, this is the first time that
this has been quantitatively assessed. Our results confirm the
importance of predicting the effect of selectively blocking the
upper soleus nerve in preoperative assessment.
In conclusion, these case reports highlight the fundamental
role of the soleus muscle in triceps surae spasticity and the
effectiveness of soleus neurotomy in spastic equinus foot.
Acknowledgement
To Drs G. Stoquart and G. Caty for their help and support during patient
assessments.

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