Biology, Medicine, & Natural Product Chemistry  ISSN 2089-6514 (paper) 
Volume 12, Number 2, October 2023 | Pages: 431-435 | DOI: 10.14421/biomedich.2023.122.431-435 ISSN 2540-9328 (online) 
 

 

 

 

Assessment of Sensorimotor Behaviour in Konzo-Induced Rats  

Using the Irvine, Beattie Bresnahan Forelimb Scale 

 

1Department of Anatomy, Faculty of Basic Medical Sciences; 2Department of Biomedical Technology, School of Science Laboratory Technology, 

University of Port Harcourt, Rivers State, Nigeria. 
 

 

Corresponding author* 
uahomoprecious1@gmail.com; Phone: +2347035313368 

 

 
Manuscript received: 24 June, 2023. Revision accepted: 26 July, 2023. Published: 12 August, 2023. 

 

 

Abstract 

 

Konzo is a neurological disorder of selective upper motor neurons. It is an irreversible paralytic disease associated with prolonged 

consumption of Cassava. It contains cyanogenic glycosides metabolized to hydrogen cyanide, which has been shown by studies to affect 

the motor neurons of the central nervous system. The Irvine, Beattie Bresnahan (IBB) scale is a recently developed forelimb scale for the 

assessment of fine control of the forelimb and digits after cervical spinal cord injury such as Konzo. 20 Adult male Wistar rats were 

assigned to 4 experimental groups (i) control n=5, (ii) konzo-induced group n=5, (iii) induced + Complan n=5 (iv) Induced + Bambara 

Nut (Okpa). The bitter cassava foods were taken by oral ingestion for a period of 4 weeks. The assessment of the forelimb and digits were 

done using the Irvine, Beattie Bresnahan (IBB) with specific parameters such as Predominant Elbow Joint movement, Contact Volar 

Support, and Grasping method. The body weight of the animals was also recorded every week. The data obtained were analyzed using 

ANOVA. The result obtained showed that there was a significant difference (p<0.05) between the body weight of the animals induced 

with Konzo and rehabilitated with Complan milk and Bambara nut when compared to the unrehabilitated Konzo-induced group. There 

were differences in the results of the parameters being tested for the Irvine, Beattie Bresnahan (IBB) scaling. The IBB scale confirmed 

that there was a high level of cyanide content in the cassava which affected the behavioral attributes of the induced group and it also 

confirmed that the induced group can be ameliorated with the use of Complan and Bambara Nut (Okpa) which was shown in the 

parameters being tested such as Predominant Elbow Joint movement, Contact Volar Support, and Grasping method. It was concluded that 

insufficiently processed bitter cassava is toxic and has neurotoxicity effects on the Spinal Cord especially on the upper motor neurons and 

IBB scale is capable of measuring gradual improvements in motor forelimb functions in this model and may be a new and effective 

assessment tool for peripheral nerve injury. 

 

Keywords: Bambara nut; Cyanogenic; Neurotoxicity; Konzo; Bitter Cassava; Irvine, Beattie Bresnahan Forelimb Scale. 

 

 

INTRODUCTION 
 

Cassava toxicity has been incriminated in the 

pathogenesis of tropical myeloneuropathies, such as 

tropical ataxic neuropathy (TAN) and Konzo. TAN is a 

progressive myeloneuropathy that was first described in 

Nigeria and is characterized by a progressive onset of 

ataxia. On the other hand, Konzo is a permanent and 

clinically distinct upper motor neuron disease of abrupt 

onset first described in the Democratic Republic of 

Congo (DRC). The word “Konzo” means tied legs and 

originated from the Yaka tribe in DRC to designate a 

fetish used by hunters to weaken legs and catch wild 

animals (Trolli, 1938; Van der Beken, 1993).   

Konzo occurs mainly in children and young women 

of childbearing age. The paralysis occurs quite suddenly, 

does not progress over time, and is irreversible. It is 

associated with the consumption of a monotonous diet of 

high cyanide (bitter) cassava, by poor rural people in 

Africa, many of whom suffer from malnutrition. 

Specifically, konzo is associated with a high cyanide diet 

of bitter cassava consumed over a period of several 

weeks combined with a low intake of protein, 

particularly a shortfall of essential S-containing amino 

acids that are needed to detoxify cyanide to thiocyanate 

in the body (Howlet et al, 1990). 

The exact pathogenetic mechanisms of the disease 

remain unknown. Epidemiological studies consistently 

show an association between outbreaks of the disease 

and chronic dietary reliance on insufficiently processed 

cyanogenic cassava (manioc or tapioca). Biochemical 

and toxicological studies suggest that the metabolites of 

linamarin (α-Hydroxyisobutyronitrile β-D-

glucopyranoside, the main cassava cyanogen), notably 

cyanide (mitochondrial toxin), thiocyanate (AMPA 

chaotropic agent), and cyanate (protein carbamoylating 

agent) may play an important role in the pathogenesis of 

Konzo. Experimental data suggest that thiol-redox and 

protein-folding mechanisms may also be perturbed. 

Factors of susceptibility including genetics, poor 

Lekpa Kingdom David1, Precious Ojo Uahomo2,*, Victor Hogan Idung2, Rachael Data Dakoru2 

https://doi.org/10.14421/biomedich.2023.122.431-435


 

 
 

432 Biology, Medicine, & Natural Product Chemistry 12 (2), 2023: 431-435 
 

 

nutrition, poverty, and dietary cyanogen exposure, or 

their interactions have been suggested.  

The Irvine, Beattie Bresnahan (IBB) scale is a 

recently developed forelimb scale for the assessment of 

fine control of the forelimb and digits after cervical 

spinal cord injury (SCI). Several experimental models of 

cervical spinal cord injury (SCI) have been developed 

recently to assess the consequences of damage to this 

level of the spinal cord (Pearse et al., 2005; Gensel et al., 

2006; Anderson et al., 2009), as the majority of human 

SCI occur here. Behavioral deficits include loss of 

forelimb function due to damage to the white matter 

affecting both descending motor and ascending sensory 

systems, and to the gray matter containing the segmental 

circuitry for processing sensory input and motor output 

for the forelimb. This is the basis for the study; hence, 

this study aims to assess the sensorimotor behaviour in a 

konzo-induced rat using the Irvine, Beattie Bresnahan 

forelimb scale. 

 

 

METHODOLOGY 
 

Animal Procurement 

Twenty (20) Wister rats weighing between 150-200g 

were acquired from the Animal House of the Department 

of Pharmacology, Faculty of Basic Clinical Sciences, 

University of Port Harcourt for this research work. The 

animals had free access to water and were fed ad libitum 
with standard feed (broiler finisher – Guinean feed). Two 

weeks before the start of the test, the animals were 

acclimated. 

 

Plant Collection and Identification  

The cassava plants were gotten at the Ministry of 

Agricultural Development Program, Rumuodomaya, Port 

Harcourt, Rivers State, and were identified by the 

Agriculture Department of the University of Port 

Harcourt, Choba, Rivers State. 

 

Processing of Bitter Cassava Root 

Fresh cassava roots were uprooted from the farm, and 

immediately after harvesting the outer layer (skin or 

cortex) was removed with a knife to expose the white 

inner layer. Then the roots were sliced into smaller sizes 

like chips and allowed to sundry for 3 consecutive days. 

The dry cassava pieces were manually grinded into 

powder form using a grinding machine and served to the 

experimental animal as cassava chow. 

 

Induction of Konzo Disease in Rats 

After two weeks of acclimatization, 15 rats were fed with 

the processed bitter cassava flour constantly to induce the 

Konzo disease and its effects. The oral feeding method 

used represents the real scenario of food being consumed 

by ingesting through the mouth, passing through the 

esophagus into the stomach following the alimentary 

canal, contacting the necessary visceral organs along 

with their associated fluids such as saliva in the mouth 

and gastric juices including any contributions provided 

via sublingual or buccal absorption during digestion. 

 

Experimental Design 

The experimental method as described by David et al. 

(2022) was used in this study. Twenty (20) albino Wistar 

rats were used for this study. Out of the 20 rats, 15 were 

induced with Konzo disease for two weeks and then 

randomly selected into three (3) groups of five (5) 

animals each (groups 2, 3, and 4), while the remaining 5 

rats without Konzo disease served as control (group 1).  

 

Rehabilitation Group: After the period of Konzo 

disease induction, Group 3 and group 4 were completely 

stopped from consuming the bitter cassava and replaced 

with rat feed and Complan milk for group 3 and Bambara 

nut (Okpa) for group 4. The mode of feeding was by oral 

ingestion. 

 
Table 1. Experimental Design. 
 

Group Identity 

N
o

. 
o

f 
R

a
ts

 

Treatment 

Group 1 Control 5 2ml Normal Saline 

Group 2 Induced Control 5 Bitter Cassava only 

Group 3 Complan 5 Bitter Cassava + Complan Milk 

Group 4 Bambara Nut 5 Bitter Cassava + Bambara Nut 

 

 

Determination of Body Weight 

The animals were weighed daily with an electric 

weighing scale (SF-400C) and the body weight of the 

rats was recorded.  

 

Sensorimotor Behaviour Assessment 

The forelimb function was assessed using a special 

method, which is IBB (Irvine, Beattis and Bresnahan 

Test). The procedure is as explained; Rats were given 

pieces of cereal in their home cage twice daily beginning 

as soon as they entered the lab. Forelimb function was 

assessed while rats were eating cereal as described 

previously (Irvine et al., 2010). Briefly, rats were 

individually placed in a Plexiglas cylinder 

(diameter = 20 cm; height = 46 cm) or in their home cage 

and they were given donut-shaped pieces of cereal that 

were of a consistent size and shape prior to the initiation 

of eating. Rats were not scored when eating cereal pieces 

that were broken prior to the initiation of testing. Each 

trial was recorded to allow slow-motion HD playback 

and evaluation of forelimb use. Videos of animals eating 

the cereal were evaluated using a standardized scoring 
sheet to record observations of forelimb behaviors, 

including joint position, object support, wrist and digit 

movement, and grasping method used while consuming 

both cereal shapes.  



 

 
 

 David et al. – Assessment of Sensorimotor Behaviour in Konzo-Induced Rats … 433 
 

 

Cyanide Analysis 

The samples for analysis of the Cyanide in the bitter 

cassava were prepared as follows: 

▪ 10g of the sample was mixed with 50ml of water in a 
corked conical flask. 

▪ Allowed to stand for 24hrs to extract the residual 
cyanoglucosides in the samples. 

▪ The mixture was subsequently filtered to obtain the 
soluble extract containing cyanoglucosides 

▪ The same procedure as with standard KCN solutions 
was followed to determine the free cyanide 

concentration (as HCN equivalent) in the sample 

filtrate. 

▪ The absorbance of the sample solution was equally 
measured at 510nm wavelength against a blank 

devoid of KCN solution. 

▪ Cyanide levels of the test samples were evaluated 
from the standard calibration curve by extrapolation. 

 

Ethical Clearance 

The experimental animals were acquired from the animal 

house of the Department of Pharmacology in the Faculty 

of Basic Medical Sciences. All procedures carried out 

during this research were done in accordance with the 

guiding principles of research involving animals as 

recommended by the Research Ethics Committee of the 

University of Port Harcourt. Animals were kept in 

standard metal cages and at room temperature.   

 

Statistical Analysis 

Data were analyzed using Statistical Package for the 

Social Sciences (SPSS IBM version 23.0) and Microsoft 

Excel 2019 edition. Values were expressed as mean ± SD 

in descriptive statistics. One-way analysis of variance 

(ANOVA) was used to analyze the difference between 

the groups followed by the Least Significant Difference 

(LSD) post-hoc test. The confidence interval was set at 

95%, and therefore p<0.05 was considered significant. 

 

 

RESULTS 
 
Table 2. Effect of Konzo disease, Complan milk and Bambara Nut (Okpa) on the Body Weight (Grams) of Wistar rats. 
 

Group Baseline Weight Week 1 Week 2 Week 3 Week 4 Mean Weight 

Group 1 263.01±5.13 263.00±5.87 265.02±6.10 260.10±6.32 273.05±6.75 265.25±2.78b 

Group 2 242.30±5.17 175.70±5.16 181.10±4.80 171.80±5.15 172.40±5.90 175.25±2.13a 

Group 3  175.25±4.87 194.10±4.21 192.50±4.11 223.10±8.23 230.10±8.40 209.95±9.72a,b 

Group 4 175.25±5.10 188.30±5.87 190.05±7.02 200.60±7.50 208.90±7.11 196.95±4.82a,b 
 

The results are expressed as mean ± SEM. Level of significance values are ap<0.05 when compared with group 1 (control), bp<0.05 when 

compared with Group 2 (konzo induced). 

 

 

 
Figure 1. Comparison of Baseline Body Weight with Final Mean Body weight of Wistar rats. 
 

 

Table 3. Irvine, Beatties and Bresnahan Forelimb Scale. 
 

Group PEJP CVS GM 

Group 1 (Control)  Flexed None Normal  

Group 2 (Induced)  Partially flexed Nearly Always Abnormal 

Group 3 (Induced + Complan)  Flexed Some Normal 

Group 4 (Induced + Bambara Nut)  Flexed Some Normal 
 

Keys: PEJP = Predominant Elbow Joint Position; CVS = Contact Volar Support; GM= Grasping Method 

0

50

100

150

200

250

300

Baseline Body Weight  Mean Body Weight

B
o

d
y 

W
e

ig
h

t 
(g

)

Duration (Weeks)

Body Weight (g)

Control

Konzo Induced

Konzo + Complan

Konzo + Bambara Nut (Okpa)



 

 
 

334 Biology, Medicine, & Natural Product Chemistry 12 (2), 2023: 431-435 
 

 
 

 
Figure 2. Contact Volar Support: A – Control (Fed with normal feeds – 

finishers), B – Fed with bitter cassava, C - fed with bitter cassava then 

treated with Complan, D - Fed with bitter cassava then treated with 
Bambara Nut  

 

 
Figure 3. Predominant Elbow Joint movement: A – Control (Fed with 
normal feeds – finishers), B – Fed with bitter cassava, C - fed with bitter 

cassava then treated with Complan, D - Fed with bitter cassava then treated 

with Bambara Nut 

 

 
Figure 4. Grasping Method: A – Control (Fed with normal feeds – 

finishers), B – Fed with bitter cassava, C - fed with bitter cassava then 

treated with Complan, D - Fed with bitter cassava then treated with 
Bambara Nut  

DISCUSSION 
 

The effect of bitter cassava has been studied extensively 

and its neurotoxicity was being studied with the use of 

experimental animal models to evaluate the effects of 

diverse substances on motor function and their 

relationship with CNS disorders. (Gerhart et al., 1982; 

Kulig et al., 1985; Fowler et al., 1990). The weight of the 

rats was taken and measured accurately from the 

beginning of the week till the end of the experiment at a 

significant value of p<0.05. It was observed that there 

was a significant difference between the mean body 

weight of the control group 265.25±2.78g and the mean 

body weight of the induced group (175.25±2.13g). The 

difference between the weight of the induced was 

different from that of the induced as a result of the intake 

of the bitter cassava which has caused a neurotoxic effect 

on the experimental models. This agrees with the 

findings of David et al. (2022) and Enefa et al. (2020). 

Some nutritional approaches were used to ameliorate 

the effect of the bitter cassava for a period of 4 weeks 

after the initial four weeks of being induced with Konzo 

disease. The nutritional approach used was Complan and 

Bambara nut (Okpa). There was a significant difference 

between the mean body weight of the ameliorated group 

and that of the induced. The Complan group had a mean 

body weight of 209.95±9.72g while the Bambara nut 

group has a mean body weight of 196.95±4.82g. This 

shows that the effect of the bitter cassava on the 

experimental models was ameliorated as there was a 

significant increase in the weight of the induced group 

after being fed with Complan and Bambara nut (Okpa). 

This is also similar to the findings of David et al. (2022) 

and Enefa et al. (2020). 

The IBB Forelimb Scale provided a sensitive 

measurement scale for detecting recovery of both 

proximal and distal forelimb function, including digit 

movements, during a naturally occurring behavior. This 

behavioral test was developed and tested in rats with 

spinal cord injury by Irvine et al. (2010). This method 

evaluated the overall integrity of rodent forelimb 

functionality during a food intake task, measuring how 

rats grasp a cereal piece. The IBB scale was used to test 

just 3 parameters which include predominant elbow joint 

movement, contact Volar support, and grasping method.  

During the assessment of contact volar support, the 

scale was rated as ‘None’ ‘Some’, and ‘Almost Always’. 

The rat was assessed for its ability to use the volar 

(palmar) surface of the impaired forepaw to stabilize the 

cereal and, in doing so, maintain a position to aid eating. 

In Figure 2, group A being the control group, no volar 

support by the forelimb during eating (<5% of the time). 

But in group 2, being the induced group that was affected 

by the cyanide content of the bitter cassava, the Volar 
support of the object occurred nearly always or always 

during eating (>95% of the time). This is because the 

Spinal Cord had been affected which in turn relates to 



 

 
 

 David et al. – Assessment of Sensorimotor Behaviour in Konzo-Induced Rats … 435 
 

 

how the rats had to use their Volar for support. The 

Ameliorated group which is group 3 (Complan) and 

group 4 (Bambara nut) had the support of the volar but 

did not occur always. This shows that the Konzo disease 

was ameliorated which helped to reduce the use of volar 

for support in the case of the induced group. 

The original scale rated the Predominant Elbow Joint 

Position as “extended, partially flexed, or fully flexed.” 

Discrimination between partially and fully flexed 

appeared to be problematic, and perhaps irrelevant in 

more recovered animals. Looking at Figure 3, the rat 

models were assessed for the most common position 

(more than 50% of the time). The elbow joint movement 

for group A was found to be flexed. Group B was 

partially flexed as a result of the cyanide content of the 

bitter cassava affecting the spinal cord. After the induced 

were ameliorated, the Elbow joint movement was flexed 

fully.  

The grasping method was rated to be ‘Normal’ and 

‘Abnormal’ according to Figure 4, the experimental rat 

models were assessed for the most common (more than 

50% of the time) grasping technique used during the 

eating phase. The rat models of group 1 were found to be 

normal with consistent use of the grasping method used 

prior to injury to support and control the cereal piece 

during the eating phase. Group 2 being induced was 

abnormal because they consistently used an alternative 

method of grasping to the method used prior to the injury 

to support and control the cereal piece during the eating 

phase. They were able to support their grasping with 

their volar. This is a result of the spinal cord injury that 

occurred as a result of the intake of bitter cassava which 

had a high percentage of cyanide content. The 

ameliorated group was found to be normal in their 

grasping method. 

According to Speck et al. (2014), the IBB scale is 

capable of measuring gradual improvements in motor 

forelimb functions in this model and may be a new and 

effective assessment tool for peripheral nerve injury. 

This was seen in this study as the induced group was 

being ameliorated with Complan and Bambara nut and 

there was gradual improvement in the motor forelimb 

function using the three parameters, Predominant Elbow 

Joint Movement, Contact Volar Support, Grasping 

method. 

 

 

CONCLUSION 
 

This study has shown that insufficiently processed bitter 

cassava is toxic and has neurotoxicity effects on the 

Spinal Cord especially on the upper motor neurons. A 

balanced diet with sufficient nutrients such as Complan 

and Bambara Nut (Okpa), can ameliorate the effects of 

konzo disease as there was no effect on motor neurons of 

the spinal cord of the animals rehabilitated with Complan 

and Bambara Nut (Okpa).  

 

Competing Interests: The authors declare that there are 

no competing interests. 

 

 

REFERENCES 
 
Anderson K., Sharp K., Hofstadter M., Irvine K., Murray M., 

Steward O. (2009). Forelimb locomotor assessment scale 

(FLAS): novel assessment of forelimb dysfunction after 

cervical spinal cord injury. Exp. Neurol., 220:23–33. 

Enefa S., Chikwuogwo W.P, Lekpa K.D. (2020). Model of Konzo 

disease: Reviewing the effect of bitter cassava neurotoxicity on 

the motor neurons of cassava-induced konzo disease on Wistar 

rats. Saudi Journal of Medicine; 5(11):336-348.  

Fowler S.C., Liao R.M., Skjoldager P. (1990). A new rodent 

model for neuroleptic-induced pseudo-parkinsonism: Low 

doses of haloperidol increase forelimb tremor in the rat. Behav. 

Neurosci., 104:449–456.  

Gensel, J.C., Tovar, C.A., Hamers, F.P.T., Deibert, R.J., Beattie, 

M.S., Bresnahan, J.C. (2006). Behavioral and histological 

characterization of unilateral cervical spinal cord contusion 

injury in rats. J Neurotrauma, 23:36–54  

Gerhart J.M., Hong J.S., Uphouse L.L., Tilson H.A. (1982). 

Chlordecone-induced tremor: Quantification and 

pharmacological analysis. Toxicol. Appl. Pharmacol., 66:234–

243.  

Howlett, W. P, Brubaker, G. R., Mlingi, N., Rosling, H. (1990). 

Konzo, an epidemic upper motor neuron disease studied in 

Tanzania. Brain, 113:223–235. 

Kulig B.M., Vanwersch R.A.P., Wolthuis O.L. (1985). The 

automated analysis of coordinated hindlimb movement in rats 

during acute and prolonged exposure to toxic agents. Toxicol. 

Appl. Pharmacol., 80:1–10.  

David L.K, Idung V.H and Uahomo P.O (2022). Neurobehavioral 

and Ameliorative Effect of Complan Milk and Bambara Nut 

on Rats Fed with Bitter Cassava – A Nutritional Approach. 

International Neuropsychiatric Disease Journal, 17(1): 7-17 

Pearse, D., Lo T Jr, Cho, K., Lynch, M., Garg, M., Marcillo, A et 

al. (2005). Histopathological and behavioral characterization 

of a novel cervical spinal cord displacement contusion injury 

in the rat. J Neurotrauma, 22:680–702. 

Speck A. E., Jocemar I., Caroline C. S., Aguiar A. S. Jr., Santos A. 

R., Swarowsky A., (2014). The IBB Forelimb Scale as a tool 

to assess functional recovery after peripheral nerve injury in 

mice. Journal of Neuroscience Methods, 226:66–72. 

Trolli, G, (1938). Paraplégie spastique épidémique, “Konzo” des 

indigènes du Kwango. In: Trolli G (Ed.), Résumé des 

observations réunies, au Kwango, au sujet de deux affections 

d´órigine indéterminée Fonds Reine Elisabeth, Brussels, pp. 1–

36.  

Van der Beken, A., (1993). In: Karthala (Ed 1.), Proverbes yaka 

du Zaire Harmattan, Paris 

 



 

THIS PAGE INTENTIONALLY LEFT BLANK