Paraparesis 2

"I've been given this case
https://hitesh116.blogspot.com/2020/05/elog-13th-may-2020.html?m=1
 to solve in an attempt to understand the topic of "paraparesis."

This may develop my competency in

a) reading and comprehending clinical data related to "paraparesis" including history, clinical findings, investigations

b) come up with a diagnosis such as:
1) Anatomical location of the root cause
2) Physiological functional disability
3) Biochemical abnormalities that could be a root cause at a molecular level
4) Pathology that could reflect the root cause at a cellular level

c) a treatment plan for each of these patients of paraparesis that can have a pharmacological and non pharmacological component.

d) learning the scientific basis of diagnostic and therapeutic approach in terms of past collective experiences and experiments (aka evidence based medicine).

Following is my analysis of patient's problem.

A 18 year old male patient presented with weakness of both lower limbs which is acute in onset.

Based on history 

There is no sensory involvement, no involuntary movements, no cerebellar involvement.So I cut done my differential diagnosis to upper motor neuron lesion and lower motor neuron lesion.

Based on examination

Findings of examination show that there is atophy, hypotonia, absent deep tendon reflexes and babinski is neagative.

Based on this finding I confine my diagnosis to LMN lesion.Now problem arises where exactly is the site of lesion as LMN involves anterior horn cell,dorsal root ganglion, spinal nerve root , peripheral nerve, NMJ, and muscle.

To know where the exact site of lesion, we need to first ask following questions:

• symmetrical or asymmetrical 
• proximal or distal
• sensory or motor
• reflexes present or absent

So by answering to the above question,in this case there is symmetrical weakness of both proximal and distal lower limbs muscles and deep tendon reflexes are absent.There is motor involvement.From this findings my differential diagnosis is myopathy and peripheral neuropathy. 

So now the aim is to know whether it is MYOPATHY OR NEUROPATHY.And if myopathy what is the main pathology. How can this be done???

First I will try to know what can be the pathology related to  myopathy in this case.So looking to the history once again we can come to know that there is persistent weakness.What can  cause persistant weakness??

     It could be due to certain type of drugs but then in this case there not history of use of them.Next what comes to my mind is hypothyroidism, for this we have to check his thyriod profile.After checking the thyroid profile, it was normal.So this possibility is also ruled out.Now we are left will inflammatory pathology such as polymyositis. For this muscle biopsy can be done.

So my differential diagnosis for this case is still left with POLYMYOSITIS and PERIPHERAL NEUROPATHY.

To know whether the nerve involvement is present or not, nerve conduction studies /EMG can done

After performing NCS it is known that there is common peroneal nerve and sural neuropathy. Physiotherapy can advised to the patient.

Now final diagnosis can be made as NEUROPATHY,  but then what happens to MYOPATHY.??Whether it can be POLYMYOSITIS ????To know about this muscle biopsy should be done.

References:

Daniel H. Lowenstein; Joseph B. Martin; Stephen L. Hauser. Approach to patient with neurological disease. In:D.L Kasper, S.L. Hauser,D.L.Longo, J.L.Jameson, J.Loscalzo, A.S.Fausi. Harrison's principles of internal medicine.20th ed. New York: McGraw-Hill;2018.Pg 3025-3030

Anthony A. Amato; Richard J. Barohn. Peripheral neuropathy. In:D.L Kasper, S.L. Hauser,D.L.Longo, J.L.Jameson, J.Loscalzo, A.S.Fausi. Harrison's principles of internal medicine.20th ed. New York: McGraw-Hill;2018.Pg 3204-3225