Vascular dementia or multiinfarct dementias

EXPLAIN IN DETAIL THE ROLE OF SPECT IN NEUROLOGICAL DISORDERS ?

A 2 INTRODUCTION

1 Is an important 2nd line test in close head injury with post injury neurological or psychiatric symptoms

2 There is a level II A evidence regarding its use in TBI

3 also kn as single photon emission computed tomography as it can identify early changes in neurological diseases such as dementia by imaging regional cerebral blood flow - provides a predictive indicator of damage

4 is of particular interest in knowing epilepsy and dementia

5 Has a potential for detecting an improved lesion in TBI as compared to CT scan and MRI

6 can detects focal areas of hypoperfusion in the brain that are discordant with the findings of CT scan or MRI

MATERIALS USED

99 m TC HMPAO and L l ethyl cysteine dimer ( ECD )

IMAGE INTERPRETATION

1 The normal adult brain shows bilateral symmetrical tracer uptake with higher activity in temporal , parietal and occipital cortexes , basal ganglia , occiput , thalami and cingulate gyrus

A ) activity in white matter and interhemispheric fissures is less

2 In the newborn , blood flow to the frontal and temporo parietal region is slightly decreased and this pattern changes by 2 yrs of age

3 Abnormal finding includes - focal or regional areas of decreased or increased tracer uptake

USES

1 Cerebrovascular diseases ( CVA ) - can detect a reduction in blood flow immediately after an acute event

A ) can be used to detect ischemic changes rapidly to prevent irreversible brain damage

B ) focal or diffuse hypoperfusion or no perfusion is the most consistent finding

C ) can identify large strokes ( DIASCHISIS Or decreased activity in remote area )

D ) if the perfusion defect in TIA persist after 1st few days - risk of stroke is higher

2 DEMENTIAS

A ) Alzheimer disease - Brain SPECT typically shows bilateral hypoperfusion of parietal and posterior temporal lobes

1 the perfusion defects are symmetric but not same in magnitude and severity

2 the most specific and consistent finding is hypoperfusion of posterior association cortices

3 temporoparietal hypoperfusion is more severe in early onset AD than late onset

4 deficit usually spreads from posterior to anterior temporo frontal lobes with progression of the disease

5 the sensitivity and specificity of brain SPECT for diagnosis of alzheimer disease is 86 and 96 %

B ) VASCULAR DEMENTIA OR MULTIINFARCT DEMENTIAS

1 are the second cause of denentia in elderly

2 Brain SPECT shows multiple focal areas of hypoperfusion randomly distributed

3 SPECT should be correlated with CT SCAN and MRI except BINSWANGER type of dementia

C ) FRONTAL LOBE DEMENTIA OR LOBAR ATROPHY OR PICK DISEASE

1 is the most important type of frontal dementia

2 Brain SPECT usually shows symmetric hypoperfusion of frontal lobes extending into cingulate gyrus

OTHER DEMENTIAS

1 AIDS DEMENTIA - brain SPECT shows randomly distributed focal or regional areas of hypoperfusion

A ) these perfusion defects presents earlier than so , SPECT is better than conventional MRI and CT scan

2 PARKINSONISM DEMENTIA

A ) Shares a similar finding of posterior hypoperfusion as alzheimer disease

B ) about 10 % develops dementia

3 HUNTINGTON DISEASE

A ) an autosomal dominant movement disorder

B ) Brain SPECT shows decreased or absent tracer uptake in caudate nucleus of basal ganglia

4 HYPOTHYROID DEMENTIA

In this , Brain SPECT shows global cortical hypoperfusion

3 EPILEPSY

A ) most complex seizures arises from temporal lobe and in 10 - 20 % of patients is refractory to medications

B ) only 40 - 50 % of extratemporal epilepsy can be treated with surgery

C ) seizures are classified into 2 - Partial or Generalised

A ) Partial is originated from given area of brain and is further subdivided into simple ( with no impairment of concentration ) and complex ( with impairment of concentration )

D ) The role of SPECT is not the diagnosis but localisation of seizure focus for surgical therapy

E ) Ideally patient should be imaged twice once in seizure free period and other in ictal period with tracer injection at a very beginning of seizure period

F ) in the interictal or seizure free period , the SPECT shows focal or diffuse hypoperfusion usually of antero medial temporal lobe and may extend till frontal lobe

G ) in ictal period there will be hyperperfusion of the temporal lobe extending to ipsilateral basal ganglia , thalamus extending till ipsilateral motor cortex and contralateral cerebellar cortex

4 HEAD TRAUMA

A ) Brain SPECT is more sensitive than CT and MRI SCAN for revealing acute injuries

B ) focal cerebral hyperemia is associated with lower mortality rate than lack of hyperemia after head injury

5 OBSESSIVE COMPULSIVE DISORDERS

A ) Brain SPECT shows hyperperfusion of anterior portion of cingulate gyrus , bilateral orbito - frontal areas and basal ganglia

B ) patients with poor insight or with schizo obsessive behaviour it shows hypoperfusion of frontal lobes and vice versa

6 Schizophrenia

A ) Brain SPECT shows hypofrontality especially during a given task , positional changes in basal ganglia related to use of neuroleptic drugs

1 also Lt side temporal lobe hypoperfusion along with ipsilateral frontal lobe

7 Panic disorder

BRAIN SPECT shows hypoperfusion of frontal lobes with yohimbine challenge

8 Unipolar depression

Brain SPECT shows hypoperfusion of prefrontal area , temporal lobes , cingulate gyrus , LT caudate nucleus , the prefrontal , limbic and paralimbic areas in unipolar
And bipolar depression

9 Psychoactive substance abuse and dependence

Brain SPECT shows dissiminated cerebral blood flow