Hemiparetic
Cerebral Palsy: Clinical Pattern and Imaging in Prediction of
Outcome
Peter
Humphreys, Sharon Whiting, and Ba' Pham
Abstract:
Background: Hemiparetic cerebral palsy (HCP) is
described as having two main forms: arm-dominant, associated
with large cortical/subcortical lesions; leg-dominant, associated
with lesions of central white matter. Epilepsy and cognitive
deficits are common in the former pattern and rare in the
latter. Some authors have recommended routine imaging studies
in children with HCP as an assessment of etiology and a predictor
of outcome. The present study compares the relative values
of clinical analysis and imaging in predicting epilepsy and
cognitive disabilities. Methods: Forty-one consecutive
patients with HCP underwent careful clinical assessment and
imaging studies (primarily computed tomography) and were followed
prospectively for the development of recurrent afebrile seizures
and academic difficulties. Results: Twenty of
the 41 patients (48.8%) were arm-dominant, 14/41 (34.1%) leg-dominant,
and 7/41 (17.1%) proportional (arm = leg). The principal imaging
findings were: arm-dominant patients - large arterial infarcts,
porencephalic cysts, brain malformations; leg-dominant - periventricular
leukomalacia; proportional - porencephaly. Arm-dominant hemiparesis
and radiologic evidence of cortical pathology were both predictive
of cognitive deficits (odds ratios 14.2 [95% CI 2.6, 75.8]
and 5.7 [95% CI 1.4, 22.3] respectively). For the
development of epilepsy, both evaluation techniques were again
predictive, with imaging findings of cortical pathology being
particularly powerful (clinical pattern OR 18.0 [95% CI
3.0, 107.7]; imaging OR 80.7 [95% CI 8.5, 767.3]).
Conclusions: In this study, the clinical pattern
of HCP and the radiological findings were both predictive
of outcome, with absence of cortical pathology on imaging
being particularly predictive for the absence of epilepsy.
While the clinical pattern, in isolation, appears helpful
in predicting outcome, our results suggest that both evaluation
tools have important roles to play in the evaluation of HCP
patients.
Résumé:
Paralysie cérébrale hémiparétique:
tableau clinique et prédiction de l'évolution
au moyen de l'imagerie. Introduction: La
paralysie cérébrale hémiparétique
(PCH) est décrite comme ayant deux formes: la forme
où l'atteinte du membre supérieur prédomine,
associée à des lésions corticales/sous-corticales
étendues, et la forme où l'atteinte du membre
inférieur prédomine, associée à
des lésions de la matière blanche centrale.
L'épilepsie et les déficits cognitifs sont fréquents
dans la première forme et plus rares dans la seconde.
Certains auteurs ont recommandé des études d'imagerie
de routine chez les enfants atteints de PCH afin d'en déterminer
l'étiologie et d'en prédire l'évolution.
Cette étude compare la valeur relative des analyses
cliniques et de l'imagerie pour prédire l'épilepsie
et l'atteinte cognitive. Méthodes: 41
patients consécutifs atteints de PCH ont subi une évaluation
clinique poussée et des études d'imagerie (principalement
par tomographie assistée par ordinateur) et ils ont
été suivis prospectivement quant à l'apparition
de convulsions non fébriles et de difficultés
scolaires. Résultats: 20/41 patients
(48.8%) présentaient la forme prédominante au
membre supérieur, 14/41 (34.1%) la forme prédominante
au membre inférieur et 7/41 (17.1%) la forme proportionnelle
(atteinte au membre supérieur = membre inférieur).
Voici les principales constatations à l'imagerie: forme
prédominante au membre supérieur - infarctus
cérébraux de grande taille, kystes porencéphaliques,
malformations cérébrales; forme prédominante
au membre inférieur - leucomalacie périventriculaire;
forme proportionnelle - porencéphalie. L'hémiparésie
dominante au membre supérieur et une pathologie corticale
radiologique étaient des prédicteurs de déficits
cognitifs {risque relatif 14.2 (IC 95% 8.5, 767.3) et 5.7
(IC 95% 1.4, 22.3) respectivement}. Ces deux techniques d'évaluation
étaient prédictives du développement
de l'épilepsie, la détection de pathologies
corticales par l'imagerie étant particulièrement
puissante {RR 18.0 (IC 95% 3.0, 107.7) pour le tableau clinique;
RR 80.7 (IC 95% 8.5, 767.3) pour l'imagerie}. Conclusions:
Dans cette étude, le tableau clinique de la
PCH et les constatations radiologiques étaient tous
deux des prédicteurs de l'évolution du patient,
l'absence de pathologie corticale à l'imagerie étant
particulièrement prédictive de l'absence d'épilepsie.
Bien que le tableau clinique seul semble aider à prédire
l'évolution, nos résultats suggèrent
que ces deux outils ont un rôle important dans l'évaluation
des patients atteints de PCH.
Can.
J. Neurol. Sci. 2000; 27: 210-219
It has long been recognized that the clinical pattern seen in
children with hemiparetic cerebral palsy (HCP) often predicts
which patients will develop cognitive disabilities and/or unprovoked
seizures, and which will not. Children whose hemiparesis involves
the upper limb to a greater extent than the lower (arm-dominant
hemiparesis) are much more likely to experience learning difficulties
than those whose clinical pattern is leg-dominant. [1,2,3]
Likewise, children with arm-dominant hemiparesis are more likely
to develop recurrent, unprovoked seizures. Those whose clinical
pattern affects the upper and lower limbs to an approximately
equal extent (sometimes referred to as "proportional" hemiparesis)
appear to fall between the arm-and leg-dominant groups in terms
of outcome. [1]
The
reason for these outcome differences between arm-dominant,
leg-dominant and proportional hemipareses appears to be related
to their respective pathological underpinnings, as suggested
by the results of imaging studies (ultrasound, CT and MRI).
Patients with arm-dominant hemiparesis tend to have relatively
large lesions involving cortex and subcortical white matter
(e.g. major arterial territory infarcts, porencephaly, schizencephaly,
polymicrogyria, cortical and subcortical atrophy) and would
therefore be more likely to develop learning difficulties
and epilepsy. [1,4,5] Conversely, children with leg-dominant
hemiparesis tend to have smaller lesions involving central
and periventricular white matter (e.g. periventricular leukomalacia
(PVL), small post-hemorrhagic porencephalies) and would be
expected to do relatively well. [1,4,5]
During
the past two decades, there have been a number of published
series of imaging studies in children with HCP which, while
not specifically correlating the pattern of hemiparesis with
imaging results, have also demonstrated a correlation between
large cortical and subcortical lesions and learning difficulties
+/- epilepsy. [6-12]
Not
all authors are in agreement with these clinical-radiological
correlations. In a prospective, follow-up study of unilateral
brain lesions identified in the pre- or perinatal periods,
Bouza et al [13] reported that follow-up MRI studies
failed to demonstrate a correlation between lesion size, severity
of hemiparesis and outcome. Likewise, Molteni et al [14]
could not demonstrate a clear-cut correlation between the
type of brain lesion revealed on CT, and the pattern of clinical
dysfunction, although there was a tendency for patients with
cortical-subcortical lesions to have more severe deficits
in the impaired hand, and a lower IQ than patients with periventricular
pathology.
On
the basis of their results, some authors have concluded that
routine imaging studies in children with HCP are useful in
predicting clinical outcome, [3,7,8,10,11] and that
MRI is preferable to CT. [5,12] While imaging studies
clearly provide useful information concerning timing and etiology
of lesions, there is no published evidence that they are more
useful than a simple assessment of the clinical pattern in
predicting outcome. Given that CT, and particularly MRI, studies
are relatively expensive investigations, it would be important
to demonstrate that routine performance of imaging studies
in children with cerebral palsy gives sufficiently valuable
information to justify the expenditure of scarce health-care
resources.
Using
a cohort of 41 patients with HCP, we assessed the predictive
value of a careful analysis of the clinical picture, and of
a radiological evaluation of brain lesion type and location
in the eventual development of academic difficulties and unprovoked
seizures. Portions of this work have been previously presented.
[15]
Subjects
and methods
Patients
Forty-one
children (26 male, 15 female) with HCP seen consecutively
in the Neurology Clinic at the Ottawa Children's Treatment
Centre (OCTC) were assessed using a standardized history,
physical examination and radiological protocol. Children were
included in the cohort if they had a unilateral static disorder
of motor control and muscle tone evident prior to the age
of two years; they had to be at least four years old at the
time of cognitive analysis. Exclusion criteria included progression
of neurological deficits over time, a history of a potentially
relevant neurological insult occurring after the age of six
months, and clinical evidence of neurological pathology below
the level of the foramen magnum (e.g. myelodysplasia).
At
the time of patient intake at OCTC (the only ambulatory treatment
facility for cerebral palsied children in eastern Ontario),
the parents were asked to complete a detailed historical questionnaire
which inquired after maternal health, family history, miscarriages,
gestational length, the presence of illness, accidents or
bleeding during the pregnancy, drug or alcohol exposure, the
circumstances of labour and delivery, birth weight and the
postnatal course. The parents' responses in the questionnaire
were verified by the neurologist at the time of first assessment
in the OCTC Neurology Clinic, with completion of any relevant
items previously left unanswered.
The
degree of sophistication of the neurological examination of
the cohort obviously depended upon the age of the child at
the time of initial assessment. While most patients were initially
referred to the clinic at the time of initial detection of
neurological disability (4-18 months of age), a few were originally
diagnosed in other centers and moved to the eastern Ontario
region later in childhood. Regardless of age, all patients
had a detailed developmental assessment, an inspection for
dysmorphic features, a gross estimation of the integrity of
visual fields by confrontation, and a careful assessment of
muscle tone and joint contractures at all levels in the affected
limbs. Once patients reached the age of six years, they also
had an evaluation of cortical sensation in the involved hand,
if intellectually capable.
During
the initial assessment, function of the upper limb on the
hemiparetic side was graded according to the following simple
schema: grade 0 - fisted hand, wrist drop, no useful function;
grade 1 - crude grasp only, no pincer; grade 2 - clumsy hand
with poor rapid finger movement but preserved pincer grasp;
grade 3 - normal hand function. At the completion of the assessment,
patients were assigned to one of three groups, for purposes
of analysis:
- arm-dominant
- spasticity and functional impairment clearly greater
in the upper limb
- leg-dominant
- lower limb primarily involved with relative sparing
of the upper limb, whose functional grade was always 2 or
3
- proportional
- those patients without clear-cut arm or leg predominance,
regardless of the upper limb functional grade.
Epilepsy
Study
patients were considered to have epilepsy if, at the time
of initial assessment or during subsequent follow-up, they
had two or more unprovoked epileptic seizures. Seizures were
not considered as contributing to the diagnostic criteria
if they were provoked by a febrile illness (temperature 38oC
or greater).
Cognitive
function
At
the time data analysis was performed, the patients were assigned
to one of three groups, depending upon their level of academic
achievement, supplemented by results of formal psychological
testing:
normal
- normal school performance to at least first grade level,
with no evidence of specific learning difficulties. Most children
in this group would not have required formal psychological
testing. A few had been assessed by OCTC psychologists because
of impulse-control problems but were not excluded from the
normal group if their verbal and performance IQ scores were
in the normal range, and if their academic achievement was
normal.
learning-disabled
- academic achievement in at least one domain (reading or
mathematics) two years or more below grade level. All children
in this group had one or more formal psychological assessments
at OCTC (typically the Wechsler Intelligence Scale for Children,
English or French versions, supplemented as necessary by
other tests). Overall IQ scores had to be within the borderline
or normal ranges to permit inclusion in this group.
mentally
handicapped - formal psychological testing results indicated
function in the mentally deficient range. Children aged
six or less had a developmental quotient of 70 or less.
These children were either in special classes in regular
schools, or attended schools for the mentally handicapped.
Radiologic
assessment
Following
the initial neurological evaluation, patients in the cohort
underwent a routine computed tomographic scan of the head,
with 10 mm axial slices. If initial results indicated, further
5 mm slices through areas of interest were obtained. Prior
to 1992, CT studies were performed using a GE 8800 scanner;
since then, a sequence of two Toshiba scanners have been utilized
(Toshiba TCT 900 SX; Toshiba X-press/GX), with the most recent
version in place for the past two years. All CT studies have
been performed at the Children's Hospital of Eastern Ontario,
adjacent to OCTC.
For
specific reasons (normal CT results, unusual clinical findings,
intractable epilepsy with consideration for surgical intervention),
four patients also had magnetic resonance imaging studies.
Routine MRI studies were not performed because the Children's
Hospital of Eastern Ontario did not possess an MRI facility
until 1997, prior to which MRI investigations were performed
in a neighbouring adult facility, and were less readily available
for non-urgent problems.
CT
and MRI results were originally analysed by a succession of
pediatric radiologists, and carefully reviewed by one of the
authors (PH). Some of the terms used in the presentation of
the radiological results require some elaboration:
periventricular
leukomalacia (PVL) - this diagnosis was established according
to the criteria of Flodmark et al. [16] The extent
of the PVL in a given patient was graded according to the
following schema: PVL1 - effacement of peritrigonal white
matter, without enlargement of the lateral ventricle; PVL2
- PVL1 findings plus enlargement of the central and trigonal
regions of the lateral ventricle; PVL3 - PVL2 findings plus
thinning of gyral white matter and of central white matter
of the frontal lobe.
infarct
- encephaloclastic lesion involving the territory of
a major cerebral artery, in whole or in part.
porencephaly
- a single cystic lesion of cerebral white matter which
may or may not connect with the lateral ventricle. Porencephalic
cysts were considered to involve, or potentially compromise
cortical grey matter if their territory included gyral white
matter adjacent to cortex. Small, periventricular porencephalies
were considered not to involve cortical grey matter.
polymicrogyria
- a pathological inference based on a characteristic radiological
picture also referred to in the literature as perisylvian
polymicrogyria (see, for example, Miller et al, 1998 [17]).
Other authors [9,11] have used the term "focal pachygyria"
to refer to the same set of findings. Patients with this
disorder have an abnormally-shaped or -oriented sylvian
fissure, with cortex in the approximate distribution of
the middle cerebral artery showing irregular, abnormal thickening
and multiple, small sulci.
For
purposes of analysis, cohort patients were assigned to one
of two groups: those with clear-cut clastic, malformative
or atrophic lesions of cortical grey matter or adjacent white
matter (CG+), and those with pathology exclusively involving
white matter (CG-).
Data
analysis
The
two outcome variables assessed were: 1) the presence or absence
of epilepsy at diagnosis or during the period of follow-up,
and 2) the presence or absence of cognitive disabilities as
revealed during the follow-up period. For most analyses, patients
with learning disabilities were combined with those having
mental handicaps, in comparison with patients having no academic
difficulties.
In
the analysis of the outcome variables, the following potentially-relevant
historical and clinical features were evaluated:
- historical
data - patient sex, side of hemiparesis, length and
course of pregnancy, delivery, and postnatal period.
- clinical
patterns - the arm-dominant group outcomes were compared
with those of the leg-dominant and proportional groups,
respectively.
- upper
limb functional grade - those patients with poor upper
limb function, regardless of clinical pattern (grades 0,1)
were compared with those having good hand function (grades
2,3). This analysis was performed to focus on those patients
in the proportional group who happened to have severe upper
limb involvement.
- radiologic
findings - the CG+ group outcomes were compared with
those of the CG- group.
Potential
risk factors were summarized for all patients and according
to outcome status for cognitive functioning and epilepsy.
Potential association between risk factors and outcomes was
verified using Fisher's exact test. We used logistic regression
to relate each risk factor to outcomes and derived the associated
odds-ratios together with their 95% confidence intervals.
To examine their interaction, we tabulated outcomes according
to combinations of major risk factors: clinical patterns,
limb function and imaging results.
Results
Patient
characteristics
Relevant
clinical data (and the imaging results) are summarized for
all patients in Table
1.
The
patients in the cohort were accrued over a 13 year period,
from 1985 to 1998. At the time of the analysis of data, patients
ranged in age from four to 26 (mean 13.8 years); 35/41 patients
were aged nine or older. Duration of follow-up ranged from
two to 13 years. Twenty-nine of 41 patients (70.7%) were born
at term (36 weeks or more), the remainder (29.3%) were premature.
Of the three clinical patterns of hemiparesis, 20/41 (48.8%)
were arm-dominant, 14/41 (34.1%) leg-dominant, and 7/41 (17.1%)
proportional.
There
was a slight overall preponderance of left hemiparesis over
right (53.7% vs. 46.3%); this trend was more obvious for the
arm-dominant group (60% left, 40% right) than for the other
two groups, where right and left hemipareses were approximately
equal.
With
respect to upper limb function, 20/41 patients had a low functional
grade (0,1) on the hemiparetic side. Of these, 18/20 had an
arm-dominant pattern; 2/20 were proportional. Arm-dominant
patients mature enough to be tested for sensory function (with
rare exceptions - cases 19, 20) had impaired cortical sensation
in the involved hand. As expected, good upper limb function
correlated with intact cortical sensation.
Although
23/41 patients had reported problems during delivery and/or
the postnatal period, only 10 of the 41 patients (24.4%) had
convincing evidence of a peri- or postnatal event as a major
contributing cause to the brain pathology. The hemiparesis
in the remaining 31 patients was assumed to date from the
prenatal period (75.6%). There was a trend towards peri- and
postnatal events occurring more often in the arm-dominant
patients (30.0%) than in the other two groups (21.4% and 14.3%
respectively).
Almost
half (20/41, 48.8%) of the patients developed recurrent epileptic
seizures. Seizures typically began at an early age, either
prior to, or within a few years of the diagnosis of cerebral
palsy (average age of seizure onset 2.89 years; range three
months - 12 years). Late-onset seizures (i.e. after age six
or at adolescence) occurred in only 4/20 patients. Fifteen
out of 20 (75.0%) of the epileptic patients came from the
arm-dominant group.
At
the time of analysis, 25/41 patients (61.0%) either had verified
learning difficulties (17 patients) or were mentally handicapped
(eight patients). Of these, 17/25 or 68.0% were from the arm-dominant
group. Overall, learning disability or mental handicap occurred
in 85.0% of arm-dominant patients, 28.6% of leg-dominant patients,
and 57.1% of the proportional group.
Imaging
results
Significant
abnormalities relevant to the hemiparesis were found on imaging
in all 41 patients. One patient (#20) had a normal CT scan,
but was found to have a pontine lesion on MRI. Although all
patients had no abnormal neurological findings on the uninvolved
side of the body, 11 (26.8%) had imaging evidence of bilateral
cerebral pathology; this was particularly common in patients
with PVL (6/14, or 42.9%) (see Figure
1A).
The
most common finding on imaging was change consistent with
the diagnosis of PVL (14 patients - see methods section for
criteria). PVL of moderate severity (PVL2) was present in
the hemisphere relevant to the hemiparesis in 11/14 patients,
while the remainder had PVL1. It is important to note that
10/14 (71.4%) of the patients with PVL were born at term with
no history suggestive of perinatal asphyxia. Three out of
four patients born prematurely had a history of perinatal
asphyxia +/- neonatal respiratory distress syndrome RDS.
Large
arterial infarcts were observed in eight patients, seven in
the territory of the middle cerebral artery (MCA) (see Figure
1B), one involving the anterior cerebral artery (ACA). As
expected, 6/7 patients with MCA infarcts had arm-dominant
hemiparesis, while the patient with the ACA infarct had leg-dominant
hemiparesis. Large infarcts were noted with proportionately
equal frequency in patients born at term, and prematurely.
Porencephalic
cysts were found in 11 patients (see Figure
1C), sometimes alone (n = 7), sometimes in association with
PVL (n = 4). Six of the cysts were large, five small. Of the
11 cysts, five were noted in patients with arm-dominant hemiparesis,
two in leg-dominant patients, and four in the proportional
group (or 57.1% of this patient group). As expected, porencephalic
cysts were seen proportionately more often in premature patients
(six, or 50.0% of prematures) than in term infants (five,
or 17.2%). Premature infants with porencephaly nearly always
had a history of a grade 4 intraventricular hemorrhage (IVH)
in the postnatal period (5/6), whereas term infants had an
unremarkable postnatal history.
Polymicrogyria
in the MCA territory was noted in three patients (see Figure
1D), bilaterally in 1/3. All of these patients were born at
term and had arm-dominant hemiparesis.
A
variety of other, less common imaging findings were also observed
(see Table 1), including unilateral cortical/subcortical atrophy
(secondary to trauma, subdurals), unilateral multicystic encephalomalacia
(bacterial meningitis), small gliotic or cystic lesions of
deep white matter, pachygyria, colpocephaly, and intracranial
calcifications (n = 3, all with intrauterine infections: toxoplasmosis,
varicella-zoster, and unknown, respectively).
With
respect to specific patterns of pathology, epilepsy was common
in patients with major arterial territory infarcts (6/8 -
75.0%), porencephaly (7/11 - 63.6%) and polymicrogyria (3/3
- 100%), but was rare in patients with PVL not accompanied
by porencephaly (1/10 - 10.0%). Learning disabilities and
mental handicap, as might be expected, were frequently present
in the same patterns of pathology which predisposed to epilepsy
(infarcts 6/8 - 75.0%; porencephaly 8/11 - 72.7%; polymicrogyria
3/3 - 100%), while PVL without porencephaly most often correlated
with normal cognitive abilities (7/10 - 70.0%). As is commonly
observed, the presence of epilepsy, regardless of imaging
findings, correlated very highly with cognitive disabilities
(18/20 - 90.0%).
Twenty-three
(56.1%) patients had evidence of significant pathology involving
cortical grey matter and/or subjacent white matter (CG+, patients
1-18, 28, 34-37); 18 (43.9%) patients had central white matter
+/- central grey matter pathology (CG-, patients 19-27, 29-33,
38-41). In the CG+ group, 18/23 (78.3%) had arm-dominant hemiparesis,
2/23 (8.7%) leg-dominant, and 3/23 (13.0%) were in the proportional
group. For the CG- group, the respective figures were 2/18
(11.1%), 12/18 (66.7%), and 4/18 (22.2%).
Statistical
and outcome analysis
Analysis
of the two outcome variables with respect to potential historical
and clinical risk factors is summarized in Table
2. None of the historical risk factors (patient sex, side
of hemiparesis, length and course of pregnancy, delivery,
postnatal history) correlated significantly with outcome,
whether in terms of cognitive deficits or the development
of unprovoked seizures. On the other hand, the differences
between the three clinical patterns for the development of
cognitive disability and epilepsy were highly significant
(p=0.003 and 0.002 respectively).
In
contrast with clinical pattern, the difference in cognitive
outcome between those with poor and good upper limb function
was not significant (p=0.11). There was, however, a significant
difference between the two functional grade groups with respect
to the development of epilepsy (p=.01).
For
the two classes of imaging finding (CG+ vs. CG-), both the
cognitive and epilepsy outcome differences were significant
(p=0.02 and p<0.01, respectively).
Table
3 outlines the odds ratios of the eventual development
of cognitive deficits and epilepsy for the main clinical and
radiological criteria under consideration. An arm-dominant
pattern of hemiparesis was highly predictive of cognitive
disability in comparison with a leg-dominant pattern (odds
ratio 14.2 (95% confidence intervals 2.6, 75.8)). The same
was true for the prediction of epilepsy (OR 18.0, 95% C.I.
3.0, 107.7). The predictive value of the arm-dominant pattern
was not impressive when compared with the proportional pattern
(cognitive disability OR 4.3, 95% C.I. 0.6, 29.2; epilepsy
OR 4.0, 95% C.I. 0.7, 24.4); for both outcomes, the odds ratio
p values were not significant (p=0.07). With respect to upper
limb function, a functional grade was not predictive of cognitive
dysfunction (OR 3.3, 95% C.I. 0.9, 12.4) but was predictive
for the development of epilepsy (OR 5.0, 95% C.I. 1.4, 20.0).
Finally,
a radiological finding of cortical grey pathology was predictive
of cognitive dysfunction (OR 5.7, 95% C.I. 1.4, 22.3), and
was very highly predictive for the development of epilepsy
(OR 80.7, 95% C.I. 8.5, 767.3).
Combining
clinical pattern and imaging findings appeared to be even
more predictive of outcome (especially arm-dominant pattern
plus CG+ imaging, and leg-dominant pattern plus CG- imaging),
but the number of cases was too small to permit a statistical
comparison.
Discussion
The
types of brain pathology, and their relative frequencies,
observed on imaging studies in this cohort of patients with
HCP were similar to those observed in most reported studies.
Change compatible with the diagnosis of PVL was the most common
finding (34% of patients), as had been noted in the studies
by Kotlareck et al, [8] Uvebrant, [2] Wiklund,
Uvebrant and Flodmark, [9-11] Wiklund and Uvebrant,
[3] Molteni et al [14] and Niemann et al.
[5] The two other common findings in this study were
porencephaly (27%), and major arterial distribution infarcts
(20%), both of which were also commonly found in the above-cited
reports, as well as those of Cohen and Duffner [7]
and Claeys et al. [1] Thus, the imaging findings in
this study appear to be representative of the population of
children with HCP, strengthening any conclusions made as to
the relative utility of imaging studies in predicting long-term
outcome.
One
of the most striking findings in the imaging results was the
common occurrence of bilateral pathology (11/41) in a group
of patients in whom one would have predicted unilateral pathology.
Bilateral findings were also noted in the CT study of Wiklund
et al [9] (13/111 patients), as well as in two recent
MRI studies by Steinlin et al [18] (8/33 patients)
and Niemann et al [5] (8/41 patients). The results
of the present study, along with those of Wiklund et al, [9]
suggest that CT may be as effective as MRI in detecting the
presence of bilateral pathology.
A
specific brain maldevelopment pattern observed in some previous
studies, [5,7,9] but not seen in this cohort, is schizencephaly.
This apparent deficiency probably reflects the fact that schizencephaly,
in comparison with PVL, porencephaly and arterial infarcts,
is relatively rare as a unilateral finding, and might not
surface in a cohort of 41 patients. On the other hand, a different,
but potentially related cerebral maldevelopment, polymicrogyria,
was observed in three patients, confirming that cerebral malformations
are a consistent component of any cohort of patients with
cerebral palsy.
A
possible deficiency of this study, particularly with respect
to the possible predictive value of neuro-imaging in cerebral
palsy, is the fact that it utilized CT as its primary imaging
resource, in an age where MRI is widely available, and potentially
more revealing. [12] It is unlikely, however, that
the performance of MRI studies on all patients would have
strengthened the predictive value of the imaging results.
Since the development of cognitive dysfunction appears, in
all published studies to date, to correlate primarily with
the extent of cerebral pathology, the detection by MRI of
subtle changes in cortex or white matter missed by CT would
probably not change the observed results significantly. As
far as the prediction of epilepsy is concerned, there was
only one patient assigned to the CG- group (patient 30) on
the basis of CT findings who developed epilepsy: it is possible
that MRI might have detected grey matter pathology (e.g. hippocampal)
in this patient and raised the specificity of a CG- finding
to 100%. Against this, however, is the possibility that MRI
studies in all the nonepileptic CG- patients might have detected
subtle grey matter changes which would have weakened the predictive
value of imaging, rather than strengthening it. On the whole,
it would appear that the main advantage of MRI over CT in
the analysis of patients with HCP is the detection of pathology
in those whose CT results are normal. As it turned out, normal
CT was a rare finding in the present study (1/41 cases).
A
second potential problem with our study is the fact that we
included patients as young as four years of age at the time
of the analysis. It is possible that some of the younger patients
might develop epilepsy or demonstrate academic deficiencies
later in childhood, if followed for a sufficiently long period.
In fact, only six of the 41 patients in our cohort were aged
eight or less at the time of the analysis. Of these, four
had already developed unprovoked seizures; two already demonstrated
evidence of learning difficulties and three were clearly mentally
handicapped. Thus, if anything, our younger patients skewed
our outcome results in the direction of increased disability
rather than the reverse.
For
our cohort of HCP patients, both clinical pattern (especially
arm-dominant vs. leg-dominant) and imaging results were highly
predictive of cognitive outcome, while upper limb functional
grade was not. Considered in isolation, without respect to
other criteria, the imaging results did not appear to offer
any distinct predictive advantage over clinical analysis.
For the prediction of epilepsy, the balance tilted in the
opposite direction: while both arm-dominant hemiparesis and
cortical grey pathology are clearly predictive for epilepsy,
the imaging results appeared to be dramatically predictive,
with an odds ratio of 80.7. In particular, the absence of
cortical pathology on imaging in our study was a powerful
predictor for the absence of epilepsy.
Thus,
while our results support the finding in previous studies
[1,2,3] that the specific clinical pattern of HCP
is predictive of outcome, they also suggest that a routine
imaging study for a new patient with HCP is worthwhile, particularly
for the prediction of the presence or absence of epilepsy.
In
our opinion, there are several reasons why an imaging study
may be helpful in a given patient with HCP:
