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 » Introduction
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Table of Contents    
CASE REPORT
Year : 2011  |  Volume : 59  |  Issue : 4  |  Page : 601-604

Neuroplasticity in hemispheric syndrome: An interesting case report


1 Department of Neurosurgery, Krishna Institute of Medical Sciences, Secunderabad, Andhra Pradesh, India
2 Department of Neurology, Krishna Institute of Medical Sciences, Secunderabad, Andhra Pradesh, India
3 Department of Neuroradiology, Krishna Institute of Medical Sciences, Secunderabad, Andhra Pradesh, India

Date of Submission12-May-2011
Date of Decision26-May-2011
Date of Acceptance20-Jun-2011
Date of Web Publication30-Aug-2011

Correspondence Address:
Manas Panigrahi
Consultant Neurosurgeon, Department of Neurosurgery, Krishna Institute of Medical Sciences (KIMS), #1-8-31/1 Ministers Road, Secunderabad - 500 003, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0028-3886.84346

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 » Abstract 

Functional hemispherectomy is an accepted treatment in hemispherical intractable epilepsy syndromes. We report a patient who had functional hemispherectomy for intractable seizures secondary to right hemispheric cortical dysplasia. Preoperatively, the patient had mild left hemiparesis and functional magnetic resonance imaging (fMRI) showed bilateral motor function lateralization to normal left hemisphere. The patient remains seizure free at 1-year follow-up, with no deterioration of motor power on left side. This report reviews physiology of neural plasticity for motor function lateralization and also reliability of fMRI in determining the functional shift.


Keywords: Epilepsy surgery, focal cortical dysplasia, functional hemispherectomy, functional magnetic resonance imaging, neuroplasticity


How to cite this article:
Krishnan SS, Panigrahi M, Jayalakshmi S, Varma DR. Neuroplasticity in hemispheric syndrome: An interesting case report. Neurol India 2011;59:601-4

How to cite this URL:
Krishnan SS, Panigrahi M, Jayalakshmi S, Varma DR. Neuroplasticity in hemispheric syndrome: An interesting case report. Neurol India [serial online] 2011 [cited 2019 Nov 13];59:601-4. Available from: http://www.neurologyindia.com/text.asp?2011/59/4/601/84346



 » Introduction Top


Functional hemispherectomy is an effective treatment for intractable epilepsy in patients with hemispherical epilepsy syndromes. The principle of epilepsy surgery is to render the patient seizure free without causing an unacceptable neurological deficit. [1] In functional hemispherectomy, disconnection would require a certain innate capacity of plasticity to be harnessed preoperatively and/or postoperatively.


 » Case Report Top


A 21-year-old male presented with intractable seizures since the age of 8 months. He had infantile spasms at the onset and used to have disabling multiple seizure types: Left focal seizures with secondary generalization, sudden head and trunk flexion associated with falls and injuries, and atonic seizures since the age of 2 years. The preoperative seizure frequency was two to three times per week, mostly in clusters at any time of the day. He had delayed motor milestones and attained walking at 2 years and language at 3 years. Left hemiparesis was noted at 2 years of age. However, the patient was independent for activities of daily living.

On neurological examination, he had left hemiparesis (4/5) with mild hand grip weakness and was ambulant. Neuropsychological evaluation showed below average IQ of 48 and a Social Quotient of 52 with behavioral problems. Ictal EEG showed epileptiform discharges with right hemisphere hemispherical onset. Magnetic resonance imaging (MRI) of brain showed an extensive right hemispheric polymicrogyria [Figure 1] and [Figure 2]. Blood oxygen level dependent (BOLD) functional MRI (fMRI) with self-paced sequential finger tapping and ankle dorsiflexion paradigms revealed lateralization of bilateral upper and lower limb motor functions to the normal left hemisphere [Figure 3] and [Figure 4]. The patient underwent a right frontoparietal craniotomy and vertical parasagittal functional hemispherectomy as described by Delalande. [2] Postoperatively, the patient did not have any worsening of his pre-existing deficits and has been seizure free (Engels Class I outcome) for more than 1 year.
Figure 1: Axial Spoiled Gradient Recalled Acquisition in Steady State (SPGR) images showing cortical thickening with polymicrogyria involving the lateral aspects of the right frontal and parietal lobes

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Figure 2: Coronal Spoiled Gradient Recalled Acquisition in Steady State (SPGR) images showing cortical thickening with polymicrogyria involving the lateral aspects of the right parietal and temporal lobes

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Figure 3: BOLD functional MRI with sequential finger tapping of left upper limb showing activation in the ipsilateral precentral gyrus

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Figure 4: BOLD functional MRI with sequential ankle dorsiflexion of left lower limb showing activation in the ipsilateral paracentral lobule

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 » Discussion Top


Functional hemispherectomy is indicated in certain congenital or acquired hemispheric epilepsy syndromes with intractable seizures: Infantile hemiplegic seizure syndrome, hemimegalencephaly, Sturge  Weber syndrome More Details, non-hypertrophic migrational disorders, Rasmussen's encephalitis, trauma, hemorrhage, and meningoencephalitic sequelae. [1] Prerequisite for functional hemispherectomy is complete hemispheric syndrome as defined by the presence of hemiplegia, hemianopsia and cerebral hemiatrophy. However, for a patient with intractable seizures and near-normal limb power, functional hemispherectomy can still be performed if the affected hemisphere has diffuse abnormality and the contralateral hemisphere is radiologically normal. [1],[3],[4] The possibility of neurological deterioration following surgery and extent of subsequent recovery depends on the extent of functional shift between the hemispheres. Our patient had a clear functional shift to the normal hemisphere seen on fMRI; probably this may explain his good motor outcome.

For a functional motor shift to the normal hemisphere to happen, the innate capacity of neural plasticity would be the key. Neural plasticity is a change in functional destination of the existing neurons, that is, a reorganization of the remaining cortical-subcortical networks and their descending projections and does not involve the generation of new neurons. The basis of neural plasticity derives from synaptic plasticity. Synaptic plasticity refers to changes in the strength of neurotransmission induced by activity experienced by the synapse in the past. Changes in the frequency or strength of activation across synapses can result in long-term increases or decreases in their strength, referred to as either long-term potentiation (LTP) or long-term depression (LTD), respectively. [6],[5],[7],[8] Neural plasticity entails increase in new synapses besides strengthening and expansion of influence by dendritic arborization. [6],[7],[8] For a given neuronal function, there are far more pathways than actually in use, which become available for the organism by opening up of dormant synapses by decrease in inhibition, increased excitability or decreased threshold of synaptic transmission. Damage to a functional area of the brain also causes loss of suppression to an associated/dormant remote area of the brain as per the theory of Diaschesis. After hemispherectomy the inhibition of the corpus callosum is stopped, hence the ipsilateral pathways can open up. Also existent is an overall hyperexcitability (also increase in neuromodulators and neurotrophins) noted after such cortical insult. This overall hyperexcitability helps neuroplasticity. [8],[9]

The theory of vacariation proposes relocalization of damaged area function by reorganization of another area of the brain. [8] The premotor cortex, supplementary motor cortex or motor cortex along with abnormal corticospinal projections on the unaffected side are areas of learned motor activity and can act as substrates to take on motor function of the affected hemisphere. For this recruitment to take place, cerebral cortical horizontal fibers play a pivotal role. By extending several millimeters, its modulating capacity extends across several columns of neurons, providing prexistant information for the emergent functional area. There may be a difference in neural plasticity recruitment as it is seen more often that the premotor and hence the cortico-reticulospinal pathway is recruited in acquired disorders, whereas in developmental disorders it is the ipsilateral motor cortex that is recruited. [4],[9],[10],[11],[12],[13],[6],[7]

This capacity of plasticity has a limiting window of opportunity which is to do with the end point of plasticity. Plasticity is postulated to occur till 7 years for language, between 5 and 16 years for frontal lobe functions and between 1and 11 years for occipital functions. [10],[14] The corpus callosum suppressive nature on the ipsilateral corticalspinal projections is maximally completed by 10 years of age. [9],[4],[13] This means delay would close the capacity of plasticity which is needed to reverse postoperative weakness. Early surgery results in better cognitive outcome by reducing the seizure-induced damage of normal hemispheric development. Also, in certain hemispheric epilepsy syndromes like Rasmussen's encephalitis and extensive Sturge Weber syndrome, progressive extensive hemispheric deficits occur; hence, early hemispherotomy is indicated before maximal deficit with gains in neurocognitive outcomes. [1],[3],[2] Having said this, gains in neurocognitive status are possible following hemispherotomy for late onset seizures andin patients with worsening focal motor deficits as a wide age range has been noted for interhemispheric transfer of language and motor function. Post hemispherectomy re-organization begins soon after surgery but can continue for as long as 1 year. [3],[4] Our patient presented with mild left-sided weakness with intact gross motor and fine motor activity much later than the stipulated time for plasticity capacity. Such patients are known to be more susceptible to have significant postoperative weakness. An fMRI, however, showed a complete shift of the motor function to normal hemisphere. This precluded his chances of postoperative deterioration. [10],[15]

The exact prevalence of shift of motor and language functions in response to congenital and acquired insults is not known. Several techniques such as intracarotid amobarbital test (Wada test), positron emission tomography, fMRI, diffusion tensor imaging (DTI), transcranial magnetic stimulation (TMS) and near infrared spectroscopy have been used to assess such shifts in individual patients. Among these, fMRI is the most popular, considering its wider availability and non-invasive nature. Till the results of careful longitudinal studies in patients with well-defined lesions and specific deficits are available, results of fMRI should be interpreted in light of other studies. Specifically, a combination of fMRI information with DTI fiber tracking or TMS may prove more accurate for this purpose. [16],[17]

Seizure outcome and cognitive performance appear to be related to the underlying pathology, being most favorable in those with acquired or progressive pathology when compared to those with developmental pathology. This is especially true with hemimegalencephaly where the outcomes are poor due to abnormality in the near-normal looking hemisphere impairing plasticity. This also seems to be the reason for better motor outcomes in perinatal strokes as compared to cortical dysplasias. [18],[2],[5] Functional reorganization following developmental or early acquired hemispheric epileptogenic lesions may lead to transfer of eloquent (including motor) functions to the normal hemisphere. Preoperative identification of this element of neuroplasticity using functional imaging represents an exciting modality in selection of candidates for major hemispheric procedures.

 
 » References Top

1.Villemure JG. Functional Hemispherotomy and Periinsular Hemispherotomy. In: Baltuch GH, Villemure JG, Editor. Operative Techniques in Epilepsy Surgery. New York: Thieme Medical Publishers. 2009. p. 138-45.  Back to cited text no. 1
    
2.Delalande O, Bulteau C, Dellatolas G, Fohlen M, Jalin C, Buret V, et al. Vertical parasagittal hemispherotomy: Surgical procedures and clinical long-term outcomes in a population of 83 children. Neurosurgery 2007;60: ONS19-32.  Back to cited text no. 2
[PUBMED]  [FULLTEXT]  
3.Daniel RT, Thomas SG, Thomas M. Role of surgery in pediatric epilepsy. Indian Paediatr 2007;44:263-73.  Back to cited text no. 3
    
4.Engel J Jr. Surgically Remediable Syndromes. In: Engel J, Pedley, Timothy A. Epilepsy: A Comprehensive Textbook, 2nd Ed. Philadelphia: Lippincott Williams and Wilkins 2008. p. 1761-70.  Back to cited text no. 4
    
5.Johnston MV. Plasticity in the developing brain: Implication for rehabilitation. Dev Dis Res Rev 2009;15: 94-101.  Back to cited text no. 5
    
6.Anatomical and physiological basis of Neural Plasticity. In: Moller AR. Neural Plasticity and Disorders of the Nervous System. 1 st Ed. Cambridge: Cambridge University Press. 2006. p. 7-41.  Back to cited text no. 6
    
7.Buonomano DV, Merzenich MM. Cortical plasticity: From synapses to maps. Ann Rev Neurosci 1998;21:149-86.  Back to cited text no. 7
[PUBMED]  [FULLTEXT]  
8.Barbay S, Zoubina E, Nudo RJ. Neural Plasticity in Adult Motor Cortex. In: Ebner FF, Editor. Neural Plasticity In Adult Somatic Sensory-Motors Systems. 1 st ed., Boca Raton, FL: CRC division of Taylor and Francis 2005. p. 155-88.  Back to cited text no. 8
    
9.Holloway V, Gadian DG, Vargha-Khadem F, Porter DA, Boyd SG, Connelly A. The reorganization of sensorimotor function in children after hemispherectomy. A functional MRI and somatosensory evoked potential study. Brain 2000;123:2432-44.  Back to cited text no. 9
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10.Graveline C, Hwang P, Bone G, Shikolka C, Wade S, Crawley A. Evaluation of gross and fine motor functions in children with hemidecortication: Predictors of outcomes and timing of surgery. J Child Neurol 1999;14:304-15.  Back to cited text no. 10
    
11.Staudt M, Grodd W, Gerloff C, Erb M, Stitz J, KraÈgeloh-Mann I. Two types of ipsilateral reorganization in congenital hemiparesis: A TMS and fMRI study. Brain 2002;125:2222-37.  Back to cited text no. 11
    
12.Maegaki Y, Yamamoto T, Takeshita K. Plasticity of central motor and sensory pathways in a case of unilateral extensive cortical dysplasia: Investigation of magnetic resonance imaging, transcranial magnetic stimulation, and short-latency somatosensory evoked potentials. Neurology 1995;45;2255-61.  Back to cited text no. 12
    
13.Binder DK. Multilobar Resections and Hemispherectomy. In: Engel J, Pedley, Timothy A, Editors. Epilepsy: A Comprehensive Textbook, 2 nd Ed. Philadelphia: Lippincott Williams and Wilkins 2008: 1879-90.  Back to cited text no. 13
    
14.Hertz-Pannier L, Chiron C, Jambaqué I, Renaux-Kieffer V, Van de Moortele PF, Delalande O. Late plasticity for language in a child's non-dominant hemisphere: A pre- and post-surgery fMRI study. Brain 2002;125:361-72.  Back to cited text no. 14
    
15.Macdonell RA, Jackson GD, Curatolo JM, Abbott DF, Berkovic SF, Carey LM, et al. Motor cortex localization using functional MRI and transcranial magnetic stimulation. Neurology 1999;53:1462-7.  Back to cited text no. 15
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16.Barbro B. Johansson. Brain plasticity and stroke rehabilitation: The Willis lecture. Stroke 2000;31:223-30.  Back to cited text no. 16
    
17.Devlin AM, Cross JH, Harkness W, Chong WK, Harding B, Vargha-Khadem F. Clinical outcomes of hemispherectomy for epilepsy in childhood and adolescence. Brain 2003;126:556-66.  Back to cited text no. 17
    
18.Van Empelen R, Jennekens-Schinkel A, Buskens E, Helders PJ, van Nieuwenhuizen O. Dutch Collaborative Epilepsy Surgery Programme. Functional consequences of hemispherectomy. Brain 2004;127:2071-9.  Back to cited text no. 18
[PUBMED]  [FULLTEXT]  


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]

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